# Can someone explain to me how to top up a reservoir (rez)? I just don't get it...



## endogarden (Apr 30, 2011)

Sorry if this has been gone over, if so please direct me to the information! I am having some trouble wrapping my head around the concept of refilling a reservoir that still has nutrient solution in it. I'm specifically referring to flood/drain ebb/flow, but any recirculating rez would apply.

Let's say for example (I made these numbers up from recent experience), I add 20 gal of RO water @ 6.8pH and 10ppm, I add 5ml per gal of MagiCal, bringing the ppm to 260. Then I add veg nutes, upping the water to 850ppm. The pH has now gone down to like 4.5pH, so I add pH Up til it's at 5.6pH, the water is now 900ppm. I feed the ladies, afterwards the rez is low, they were thirsty. 

Now I want to refill it, but (unlike I currently do), I don't want to empty the remaining solution. I cannot figure out how anyone is calculating their nute solution if you add more than one liquid to your rez, which I'm guess most people are doing.

So now I check the rez, say it's 6pH and 930ppm now. I add water to the rez, filling it back up to 20 gal. Now I check the pH and ppm, the ppm is now like 230ppm, like 6.4pH. 

Of what is this 230ppm comprised? How can I possibly calculate the ratio of MagiCal I should leave out to compensate for the bit that remains in the rez from the original rez dosing? I want to have 250ppms of Calcium, Magnesium, and Iron from the MagiCal, how can I measure this if the solution has been diluted?

Please enlighten me as to how anyone and everyone are topping up their reservoirs. I'm guessing it's a simple thing I've over looked.


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## CoreyPKGrower (Apr 30, 2011)

Hmmm... I used to be very anal about precise PPM values but found I was chasing my tail. Whats works best for me is a percentage of nutrients to water. Example. 100gal res. water only. Added 10ml/gal of Micro = 100ml total. 
Knowing the reservoir is 100gal. If after watering The reservoir now has 80 gal left. Thats a 20% usage. So Now I top up tank with 20gal water and add 20ml of Micro. The PPM stays the same.... Or should on a flood and drain.


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## cannibisox (Apr 30, 2011)

I normally top my reservoir off with distilled water, Plants tend to absorb more water than actual nutrients so you're left with a more potent nutrient solution and less water, so you just top off with water. However if your PPM readings are saying something else, then that's what I would go by but make sure your meter is working properly or maybe recalibrate it.


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## Neumann (Apr 30, 2011)

endogarden said:


> Sorry if this has been gone over, if so please direct me to the information! I am having some trouble wrapping my head around the concept of refilling a reservoir that still has nutrient solution in it. I'm specifically referring to flood/drain ebb/flow, but any recirculating rez would apply.
> 
> Let's say for example (I made these numbers up from recent experience), I add 20 gal of RO water @ 6.8pH and 10ppm, I add 5ml per gal of MagiCal, bringing the ppm to 260. Then I add veg nutes, upping the water to 850ppm. The pH has now gone down to like 4.5pH, so I add pH Up til it's at 5.6pH, the water is now 900ppm. I feed the ladies, afterwards the rez is low, they were thirsty.
> 
> ...


Congratulations! You've hit the wall! What you're having is the same problem every hydro user comes up against. As far as I know NOBODY has successfully answered that question. There are different strategies, I'm sure you've researched them but what it all boils down to is, once the plants have taken in any nutrients, all bets are off for re-topping.

I can tell you what I do but it's only my preference, not The Way To Do It.


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## PeaceFarmer (Apr 30, 2011)

Isn't that the reason for completely flushing and changing your rez every week (or two)? I simply use a sharpie to draw a line to where the water should be in the rez, everyday when my pump is OFF, I check the level, if it is low I top it off with enough water to bring it back up. I then adjust the ph and check EC values. Usually my 8 plants consume 5 gallons of water a week (consumption and evaporation of h20 out of the Rez). I add fresh h2o and nutes every Monday, so that I never have to worry about the EC during the week and don't have to worry about ratios, ppm, etc. Oh, I'm growing organic aero, but I'm sure it would work the same in a hydro set up.


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## TurboKafer (Apr 30, 2011)

PeaceFarmer said:


> Isn't that the reason for completely flushing and changing your rez every week (or two)? I simply use a sharpie to draw a line to where the water should be in the rez, everyday when my pump is OFF, I check the level, if it is low I top it off with enough water to bring it back up. I then adjust the ph and check EC values. Usually my 8 plants consume 5 gallons of water a week (consumption and evaporation of h20 out of the Rez). I add fresh h2o and nutes every Monday, so that I never have to worry about the EC during the week and don't have to worry about ratios, ppm, etc. Oh, I'm growing organic aero, but I'm sure it would work the same in a hydro set up.


I agree with not over thinking and a simple fill up. When I grew in soil I thought that hydro was difficult and too much work. The truth is hydro/aero can be easy if you relax and don't make it difficult. Your concern is well founded but it is nearly impossible to gauge what your levels are past the point at which they were mixed. 

Some growers use a top off mix that is a 1/3 strength but it's up to you.


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## MEANGREEN69 (Apr 30, 2011)

a 20 gal rez isnt that big. so you can find out what it takes ( nutes,Ph-up, cal/mag what ever) to fix a

1 or 5 gal jug. make sure you let it sit for AT LEAST 30 mins after mixing it up.

cause the Ph can change. then you can have it down to a science...see i know that it takes 3ml of Ph-

down, 5ml of cal/mag, 1 tsp of maxi grow for every gal of water to get it were i want it for veg. then

if i need more just mutiply..just my 2cents hope i helped.


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## PeaceFarmer (Apr 30, 2011)

I know my first post up there didnt technically answer your question, rather just offered my opinion. So, if you wanted to be technical you could use a little bit of algebra to figure it out. I personally wouldn't do it this way just for the extra work it would take, but they are your ladies. So, say you only wanted to change your rez every 4 weeks or perhaps never. In order to top off with a solution that contains the ideal amount of nutrients, you must first determine the ratio of the original chemicals you have added. You add 250 ppm of Magical and 600ppm of Veg nutes (I omit the negligible 50 ppm from the ph up, as this value will change as your system begins to equibrilate and become steady). This means that you add 1 part Magical to every 4 parts of nute solution. So if your original ppm is 900 and your new value is 230ppm, you have a 670ppm deficit to correct. You should add 1 part of Magical and 4 parts of nutes (tsp or ml you will have to determine your own measuring value you wish to use, based on how big of an increment you want your ppm to change. For example you could make your units ml/tsp and obtain a very small change or use tbs and get a huge jump). Retest your rez solution and see what the ppm is. Get this value close, but under the 900 ppm you require. Now, add your ph down as needed to get your solution into the 5.8-6.2 range. 

BIG UNKNOWN VARIABLE: Plants consume different amounts of supplements as it grows. During veg it may consume large amounts of NPK and rather small amounts of your CalMag. This could cause your ratio to begin to vary in your solution. For this reason, you should do a regular flush and get some fresh nutes/h2o in there. If you are an experienced grower, and can easily recognize the signs of nutrient deficiency by specific plant response, then it will be easy for you to do. You could start with your basic ratio, and then if you notice leaf curling or nute burn signs, you could back off the nutes and add a little water to dilute out the solution; same thing for the cal/mag with discolorations, etc. Check daily and adjust as needed. However, I still say to just change it out every 2 weeks or so, just so you can flush the salts out to prevent a nute lockout (I use Sledgehammer).

Hope this helps better than my first post.


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## lordjin (Apr 30, 2011)

Technology can solve almost any problem. And for the lazy grower, automation is ideal.

While I agree with some of the other growers who say it's simply a method of working out your own routine, a float switch goes a long way. I just have an automatic topper that pumps fresh water from an external res every time the water level drops. This, of course, makes the ppm drop steadily, so I inject the res with the same nutrient mixture (saved in a jar as a concentrate) to get the ppms back up. I then add the appropriate amount of ph up fluid to balance. 

Topping with a diluted solution doesn't work well with an automated external reservoir...it's just one more pump to get mucked up with gunk. Topping with pure water and manually injecting concentrate allows for greater control in my opinion.

Honestly, I would die without my float switch. I have no idea how so many of you guys live without one.


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## endogarden (May 2, 2011)

lordjin said:


> Technology can solve almost any problem. And for the lazy grower, automation is ideal.
> 
> While I agree with some of the other growers who say it's simply a method of working out your own routine, a float switch goes a long way. I just have an automatic topper that pumps fresh water from an external res every time the water level drops. This, of course, makes the ppm drop steadily, so I inject the res with the same nutrient mixture (saved in a jar as a concentrate) to get the ppms back up. I then add the appropriate amount of ph up fluid to balance.
> 
> ...


Okay I totally feel you, I have a float switch in my 130gal ro tank to auto fill it, and I also have float switches in my three 27 gal nute rezs. 

How do you get the water rez to refill the nute rez (or rezs in my case)? Gravity? A pump that's electrically connected to the float switch? Currently I use a pump that I have to plug in to refill the rezs.

Also, when do you inject the solution, and is it the original solution you would put in a fresh rez, or a modified one to account for the increased level of ppm (compared to a fresh rez filling)?


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## endogarden (May 2, 2011)

PeaceFarmer said:


> I know my first post up there didnt technically answer your question, rather just offered my opinion. So, if you wanted to be technical you could use a little bit of algebra to figure it out. I personally wouldn't do it this way just for the extra work it would take, but they are your ladies. So, say you only wanted to change your rez every 4 weeks or perhaps never. In order to top off with a solution that contains the ideal amount of nutrients, you must first determine the ratio of the original chemicals you have added. You add 250 ppm of Magical and 600ppm of Veg nutes (I omit the negligible 50 ppm from the ph up, as this value will change as your system begins to equibrilate and become steady). This means that you add 1 part Magical to every 4 parts of nute solution. So if your original ppm is 900 and your new value is 230ppm, you have a 670ppm deficit to correct. You should add 1 part of Magical and 4 parts of nutes (tsp or ml you will have to determine your own measuring value you wish to use, based on how big of an increment you want your ppm to change. For example you could make your units ml/tsp and obtain a very small change or use tbs and get a huge jump). Retest your rez solution and see what the ppm is. Get this value close, but under the 900 ppm you require. Now, add your ph down as needed to get your solution into the 5.8-6.2 range.
> 
> BIG UNKNOWN VARIABLE: Plants consume different amounts of supplements as it grows. During veg it may consume large amounts of NPK and rather small amounts of your CalMag. This could cause your ratio to begin to vary in your solution. For this reason, you should do a regular flush and get some fresh nutes/h2o in there. If you are an experienced grower, and can easily recognize the signs of nutrient deficiency by specific plant response, then it will be easy for you to do. You could start with your basic ratio, and then if you notice leaf curling or nute burn signs, you could back off the nutes and add a little water to dilute out the solution; same thing for the cal/mag with discolorations, etc. Check daily and adjust as needed. However, I still say to just change it out every 2 weeks or so, just so you can flush the salts out to prevent a nute lockout (I use Sledgehammer).
> 
> Hope this helps better than my first post.


Yup that variable is the thing that gets me. What confuses me is when I feed all three of my flood tables the same thing, and a few plants on different tables, on each table, show different deficiencies. Some leaves are turning a gradient of dark pink/purplish to yellow, which I think is cal mag related, some have a few "rust spots" on the lower leaves, some colas have 3 or so completely yellow fan leaves (some colas have all deep green fan leaves), some look absolutely perfect. I can't determine why there is such a broad range of minor issues, the overall is doing great, but it's peppered with minor random-seeming issues. It's Week 7, Day 5, so 54 days flowering.

It's seeming like the top up strategies seem to involve trying to maintain a decent solution for a week, then renewing it. So it's like a week long stretched drain to waste, instead of a one feeding session drain to waste, in a way.


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## endogarden (Jul 9, 2011)

Okay, I may have figured this concept out just now. [THREAD UPDATE]

I have a 55gal barrel for a rez now, fuck the 3 27gal tote rezs I was using, those are gone. I filled my rez to 50gals (for easy math) and added all my lovely plant liquids until it got to 900ppm, then I fed, then I was left with 15gal of 900ppm solution. 

So then I waited 2 days, and now I topped up the 15gal with RO water until it was at 50gal again, meaning I have added 35gal of unaltered RO water to the mix. 

Then I just calculated my nutrient ml-to-gal ratios with 35 instead of 50 (like I would for a full rez). 

I then raised the ppms to 1000 (by adding more FloraNova Bloom), then added 0.5ml per gal aka 25ml of HCO Gravity to the mix, as I am 2 days from hitting week 4.

I think I got it, it was just too hard to grasp with 3 different rezs doing 3 different things. Damn that sucked. Now everything's awesome, and soon I will get a CAP Ebb & Gro Controller bucket to flood/drain my 3 trays sitting on the floor, so I won't have to hand water any longer.

Edit: Oooo I just realized that the only reason this works is because it is drain to waste. If it was recirculating, then the plants would absorb different amounts of different nutrients and the solution that returned to the rez would not contain the same ppm of each nutrient as it did going in. So then the top up mix would be off/variable again. So perhaps I won't get the control bucket after all. 

I have been thinking of doing an experiment where I just put airstones in the trays, and have float valves in the trays at about 1.5" above the bottoms of the root pots, having the 55gal rez gravity feeding all 3 trays continuously through the float valves, allowing the plants to drink as much as they wanted from the bottom up, soaking up through the coco coir filled, root pot bottoms. This solution would always be kept at 1.5", and aerated. This way I would never have to manage the plants nutrients, just provide ample amounts of them at the right times. My hypothesis is that the plants would select what they needed and be very healthy. 

What do you guys think?


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## MEANGREEN69 (Jul 9, 2011)

good to hear you figured it out...i like the idea of the airstones in the trays. i have wanted to do something like that for a while. but was thinking of just letting the trays stay flooding and draining with the airstones running 24/7.. was thinking of getting those big round ones ( about 3 inches) and setting them in pot before i transplant, i often use JUST perlite as a medium. i think it will breath well. if you do end up doing this make a thread i whould like to check it out for sure.


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## hellraizer30 (Jul 9, 2011)

first off 20is gal res aint going to get you much time so if I were you upgrade to a 50gal this if your plant count is under 25 will buy you a week
without add back, during add back add plain water check ppms take that number whaterever it is? then take your normal feeding formula and start
in small amounts till you get your target ppm# you want. then add your ph down or up to get your 5.8 in total you should add back once a week
and total res change every 2 week. if you still have issue hit me up


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## endogarden (Jul 9, 2011)

MEANGREEN69 said:


> good to hear you figured it out...i like the idea of the airstones in the trays. i have wanted to do something like that for a while. but was thinking of just letting the trays stay flooding and draining with the airstones running 24/7.. was thinking of getting those big round ones ( about 3 inches) and setting them in pot before i transplant, i often use JUST perlite as a medium. i think it will breath well. if you do end up doing this make a thread i whould like to check it out for sure.


Will do. I got the idea from a Maximum Yield article (http://issuu.com/maximum-yield/docs/my_usa_may_2011?viewMode=magazine&mode=embed go to Page 96) where they say: 

"What is the final answer? Use a hydroponic growing system that maintains a constant level of nutrient solution in the base of rooting vessel, and a rooting medium of perlite, composted milled pine bark, or possibly even rockwool or coir - substances that have long-term physical and chemical stability as well as a 'wicking' characteristic. The plant itself is now in control, absorbing water and nutrient elements from a constantly maintained rooting environment, and requiring a nutrient solution with a low elemental concentration (ppm). The major advantage when using this system is that all of the applied water and nutrient elements are utilized by the plant. There is also a better chance that plants growing under such conditions will remain in a condition of nutrient element sufficiency, and will be more likely to reach their maximum biological potential."



hellraizer30 said:


> first off 20is gal res aint going to get you much time so if I were you upgrade to a 50gal this if your plant count is under 25 will buy you a week
> without add back, during add back add plain water check ppms take that number whaterever it is? then take your normal feeding formula and start
> in small amounts till you get your target ppm# you want. then add your ph down or up to get your 5.8 in total you should add back once a week
> and total res change every 2 week. if you still have issue hit me up


Well I was using 3 20gal rezs, filling each and feeding one tray with each one, ebb+flow style. I then had to drop the trays and go to drain to waste because of height issues. So then I was refilling three 20gal rezs every time I fed and it was a huge PITA. So I got a 55gal barrel to replace all 3 rezs and now everything is going well, instead of using around 45 gal in 3 rezs to feed, I am now using 35gal to hand-hose feed 3 trays. So it doesn't really buy me any time, but everything is working much better and I have a much better handle mentally on the problem.


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## hellraizer30 (Jul 9, 2011)

well it would get you time if you were on a recycleing but drain to waist isnt what your threads about. owell


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## endogarden (Jul 9, 2011)

hellraizer30 said:


> well it would get you time if you were on a recycleing but drain to waist isnt what your threads about. owell


Don't get me wrong, thanks for the input, and I wasn't negating your insight into saving time, I was just relaying my current situation.


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## hellraizer30 (Jul 9, 2011)

its cool glad you got it all worked out


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## karmeron (Jul 9, 2011)

you can also use the lucas formula with his top up calculator formula, seems to work for a lot of people including myself.


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## johnwest221 (Jan 8, 2020)

[quate]

When replacing water, you’ll want to replace the nutrients in it too, especially after your plants mature and start drinking more than a gallon of water a day. In the beginning, you can probably get away with topping off your water with plain, pH’ed water. You can figure out how much nutrients to add to your top-off water by applying the following formula: Take the number of gallons you’re putting back in the reservoir, and divide that number by the total number of gallons in your reservoir. So, if you’re adding in 1 gallon, and your total number of gallons is 5, your number is 1/5. The resulting number is the fraction of your normal nutrient dose you’ll need to put back in the tank (I always like to put a little less than whatever number I ended up with). If you end up with a fraction of 1/5 like in the example, you’ll add 1/5 of your normal nutrients (or a little less) to the 1 gallon of water that you’re using to top off the reservoir.
The easier way to do this is to make an extra batch of nutrient water and use that to top off your reservoir. Nutrient water can last for at least 2 weeks after being mixed.

Minerals will build up in the reservoir and your plants may not use all the nutrients equally, so you’ll definitely want to change the entire reservoir of water *at least once every 7 days.*
The plants like the 10-15min of oxygen they get while you’re changing the water, but don’t let any of the roots dry out.









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## sandman83 (Jan 8, 2020)

Good info, really old thread though


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## Keesje (Jan 8, 2020)

johnwest221 said:


> Minerals will build up in the reservoir and your plants may not use all the nutrients equally, so you’ll definitely want to change the entire reservoir of water *at least once every 7 days*


This depends on the size of your reservoir of course (related to the amount of plants or surface)
When you have a really large reservoir for just a small amount of plants or small surface, it will take much longer before ther will be an imbalance of elements in your nutrients solution.
So then theoretically you can change your res just before the nutes start to smell funny.



johnwest221 said:


> The plants like the 10-15min of oxygen they get while you’re changing the water, but don’t let any of the roots dry out.


It will take a while before roots really dry out. Then can survive without water for several hours. Not that it is a good idea perhaps, but no need to hurry (and make mistakes) while changing the water.


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## HolyAngel (Jan 8, 2020)

> The easier way to do this is to make an extra batch of nutrient water and use that to top off your reservoir. Nutrient water can last for at least 2 weeks after being mixed.
> 
> Minerals will build up in the reservoir and your plants may not use all the nutrients equally, so you’ll definitely want to change the entire reservoir of water *at least once every 7 days.*


This is basically what I do, I make double the amount of water my res needs in a separate tote, I ph it, nute it, etc. only thing I don't add is any humic/fulvic acids and bennies. I drain my res and clean it and then refill it from this extra tote and just add the acids/bennies during the refill. Then during the week when I need to top off, I know my water is already good and don't have to worry about it, just fill it up from the extra tote and add acids/bennies as needed per amount added. After a week or so I drain them both and redo it all again. Usually I do the extra tote a day ahead of the res drain/refill.


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## Aqua Man (Jan 8, 2020)

Top up with 33% solution adjust as needed and do a res change once you have added back the volume of your system to prevent nutrient imbalances.

If your ppm is is dropping after this bump up the solution and plants likely would benefit from an overall increase in ppm of the system.

If your ppm is increasing after this you likely feeding to high of ppm.

It will never be perfect but shoot to get close and adjust adback to steer ppm, should not have issues


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## Keesje (Jan 9, 2020)

Aqua Man said:


> Top up with 33% solution adjust as needed and do a res change once you have added back the volume of your system to prevent nutrient imbalances.


Could you explain this more in detail please.
I also struggle with what is the best method.
For example: why not top up with the same solution as the original solution in the res?


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## myke (Jan 9, 2020)

This is a good topic,Ive found my plants and my pH are much happier when my top offs are 1/3 rd of my res ppm.


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## SuperiorBuds (Jan 9, 2020)

johnwest221 said:


> Minerals will build up in the reservoir and your plants may not use all the nutrients equally, so you’ll definitely want to change the entire reservoir of water *at least once every 7 days.*


I've been hearing "change the reservoir every 7 days" for 20 years now. It was the one part of my hydro system that I hated -- I didn't want to dump good nutes down the drain...ever.

This current run I rebuilt my entire system and part of that was the Torus Hydro for pH management. One side-effect of this is that it does ion-exchange to keep the pH in check instead of adding an acid or base to the mix. For the first time ever I ran an entire veg run from seed w/o a single reservoir change. There were no signs of lockout, the reservoir didn't smell and the solution was still crystal clear like the day I mixed it.

I do top-offs every 2-3 days. I refill my reservoir with RO to my "full line" and then use the flow meter to see how much water was added. From there I do the math and add the nutrients at full strength for however much water I added. (I have concentrated Jacks 321 A and B premixed and always ready to go.)


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## Keesje (Jan 9, 2020)

SuperiorBuds said:


> I do top-offs every 2-3 days. I refill my reservoir with RO to my "full line" and then use the flow meter to see how much water was added. From there I do the math and add the nutrients at full strength for however much water I added. (I have concentrated Jacks 321 A and B premixed and always ready to go.)


So no 33%.
Let's say you add 20 gallon. You use the same amount of nutrients that you normally would use if you would have a reservoir of 20 gallons?


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## HolyAngel (Jan 9, 2020)

Keesje said:


> So no 33%.
> Let's say you add 20 gallon. You use the amount of nutrients that you normally would use if you would have a reservoir of 20 gallons?


yeah you would just dose the amount of water you added with the amount of nutes you need. So like this

Start of week, 20gal res
dosing nutes at 3ml/gal = 60ml of nutes
lets say ppm is 600 and is either staying the same or slowly dropping over the week

after a week your res is half full, still hovering around 600ppms, you need to add 10 gallons to get it back to full 20gal res. 
You add 10 gallons of water
Well now your ppm's are half(300ppms) of what they were before you topped off so you have to add some nutes to get it to roughly the same level as it was before. You know you added 10 gallons of water and you know you were dosing at the start of the week at 3ml/gal and the ppm's were holding steady or slowly dropping which is what you want.
You would add 30ml of nutes(3ml/gal x 10 gallons) to get your ppm's back up to the same level they were at the start of the week.

Sometimes you need to add a little less nutes if ppm's have been rising all week, sometimes you need to add a bit more if ppm's were falling quickly every day but that's basically it.


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## SuperiorBuds (Jan 9, 2020)

Keesje said:


> So no 33%.
> Let's say you add 20 gallon. You use the same amount of nutrients that you normally would use if you would have a reservoir of 20 gallons?


Correct.

I could also do it like this, if I wanted... If my reservoir needs 20 gallons I could mix up a batch of 20 gallons of RO w/ full strength nutrients and add that into the reservoir. (I did this for many years.) The problem I found with that is I'd mix up 20 gallons, and end up only needing 18.


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## myke (Jan 9, 2020)

So I guess theirs a diff if you ad top up once a week or every 2 days. Different size systems I guess. I’m kinda anal about keeping level the same.probably makes no difference though.


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## Keesje (Jan 9, 2020)

SuperiorBuds said:


> This current run I rebuilt my entire system and part of that was the Torus Hydro for pH management. One side-effect of this is that it does ion-exchange to keep the pH in check instead of adding an acid or base to the mix. For the first time ever I ran an entire veg run from seed w/o a single reservoir change. There were no signs of lockout, the reservoir didn't smell and the solution was still crystal clear like the day I mixed it.


What you call a 'side-effect' of the Torus Hydro (keeping the pH in check) is the main purpose of such a device, as I understand from their website.
In what way do you think it helps the EC of the nutrient as well?


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## Aqua Man (Jan 9, 2020)

Keesje said:


> Could you explain this more in detail please.
> I also struggle with what is the best method.
> For example: why not top up with the same solution as the original solution in the res?


Ok so this is a guideline that should be close if the starting ppm is in the prime zone.

For me I like to see a slight increase in ppm as the plants drink not much but just a bit. But if I too up with just water the ppm goes way down pretty quickly.

33% is a good starting point but will need adjusted and will never be perfect you will always have to adjust if you are shooting for perfect numbers but if you system ppm is in the sweet spot for stage of growth then it should be close enough to get you to the next res change without much of a ppm change at all.

I do a 25-50% change at a time but that's for different reasons and I won't go into as it complicates things from what your asking.

So if you add back a 33% solution and the ppm is the same that's about where ya wanna be in a perfect world IME. Now this changes later in flower but I'm talking about veg and most of flower excluding the last 3 weeks.

If after adding back the ppm is lower you can raise the overall ppm of the system. I don't like to do more than 10-20% increase in ppm at a time but you will find you are slowly almost constantly increasing the ppm until after stretch. This is because of the growth rates and changing needs of the plants. So if you find you need to up the ppm I do so through my add backs so sometimes I may add back say 66% or more to adjust the res ppm then add back 33% next day and see where I'm at. It's all a guideline no hard fast rule. But it allows you to see and adjust the overall plant needs for concentration daily. Rather than do a res change and increase the ppm once a week it's more gradual and constant keeping the ideal ppm very close to ideal if that makes sense. By doing daily tops up with ppm check after adding back 33% you can see if you need a higher overall ppm which is usually the case once things get past week 2 you see almost daily need for a slight increase and this is why 33% is not a rule but a guide or a target per se.

If you add back 33% and the ppm is almost the same you know you are very close to being right on target for the plants. Of course it Varys with strains etc but it's a good place to start and then fine tune based on the ppm changes and plant responses.

Once you add back the volume of your system then do a complete res change out. For me it's almost 3weeks to a month before my first one and gets to as much as 5days by end of stretch. That prevents nutrient imbalances and prevents wasting a shit ton of nutes on unnecessary water changes

Not sure if that answers your question but if not just ask again.


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## Keesje (Jan 10, 2020)

I am still confused. Hahaha. I am confused about what you mean with '33%".

I will give it another try.
Let's say you have a res of 60 gallons with an EC of 1.2
After a few days 20 gallons are gone and there is still 40 gallons in the res.

Now there are 2 options:
1. You make a new batch of 20 gallons with an EC of 1.2 and with that you refill your res. (33% of the the res is now new water)
The EC in the refilled res will be around 1.2 (40 gallons with 1.2 and 20 gallons with 1.2 = average of 1.2)

2. You make a new batch of 20 gallons with an EC of 0.4. (33% of the amount of nutrients) 
The EC in the refilled res will be around (40 gallons with 1.2 and 20 gallons with 0.4 = average of 0.93)


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## kmog33 (Jan 10, 2020)

Holy balls this is an old thread.

to top off water:
Add fresh water to evap nute mix in res to same level as initial solution level....
Done


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## HolyAngel (Jan 10, 2020)

Keesje said:


> I am still confused. Hahaha. I am confused about what you mean with '33%".
> 
> I will give it another try.
> Let's say you have a res of 60 gallons with an EC of 1.2
> ...


IMO it should always be option 1. You want to keep the ppm levels the same throughout the grow for the levels you need. If the plant is keeping ppm's stable throughout the week then when you top off you need to keep roughly that same ppm level, if the ppm's are dropping before top off then you need the ppm's a little bit higher when you top off. If the ppm's are rising then you need to lower the ppm level when you top off.


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## Aqua Man (Jan 10, 2020)

HolyAngel said:


> IMO it should always be option 1. You want to keep the ppm levels the same throughout the grow for the levels you need. If the plant is keeping ppm's stable throughout the week then when you top off you need to keep roughly that same ppm level, if the ppm's are dropping before top off then you need the ppm's a little bit higher when you top off. If the ppm's are rising then you need to lower the ppm level when you top off.


Yes but you also need to adjust for the increased needs of the plant as it grows. That's what I'm talking about including here. Sure you can just go by a guideline but why not go one step further and make sure your plants are getting the right ppm. This is done by monitoring the amount they eat and doing top ups and ppm readings daily or every other day.


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## HolyAngel (Jan 10, 2020)

Aqua Man said:


> Yes but you also need to adjust for the increased needs of the plant as it grows. That's what I'm talking about including here. Sure you can just go by a guideline but why not go one step further and make sure your plants are getting the right ppm. This is done by monitoring the amount they eat and doing top ups and ppm readings daily or every other day.


yep I agree, I personally take ph and ppm readings morning and night and adjust daily as needed.


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## Aqua Man (Jan 10, 2020)

Keesje said:


> I am still confused. Hahaha. I am confused about what you mean with '33%" and likely more than 100% in order to raise the overall ppm of the system.
> 
> I will give it another try.
> Let's say you have a res of 60 gallons with an EC of 1.2
> ...


Ok so you have a 40 gal res and say daily you plants are drinking 10gal. Your EC is 1.2.

You mix up 10 gal with 33% concentration. 0.4 add it back to the res. Your EC is 1.2 after add back.. your perfect.

Your EC is 1.3 your res solution of nutrients at 1.2 EC is to high for the plants and the next add back will be used to lower the over all EC of the res.

Your EC is 1.0 your res solution of nutrients at 1.2 is to low and your next add back will be higher than 33% to increase the overall concentration of the system.

If they are drinking 10gal a day and you have a 40gal system. After 4 add back you will dump and make a fresh res.

Now like I say this is a guideline. Not a hard rule. You will see that different strains actually require different overall concentrations as they may be heavy or light feeders. This just gives a method of evaluation for you overall nutrient concentration and shows the plants feeding habits. Rather than some arbitrary number you are using the info your plant is giving you to adjust the feed according to its needs if that makes sense


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## Aqua Man (Jan 10, 2020)

HolyAngel said:


> yep I agree, I personally take ph and ppm readings morning and night and adjust daily as needed.


I'm keeping it simple here but I also do the same. Readings before and after add backs.


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## kmog33 (Jan 10, 2020)

You don’t top off with new nutrient solution. That’s fucking dumb. You’re intentionally throwing your mix off balance hoping the plant hasn’t totally destroyed one part in your older solutions because you will end up crazy imbalanced or tox, even at low ec/ppm.

The right way:

1. take fresh water(0ppm)

2. add to your res to reach its original water level. Only do this once or twice as you will end up fucked for ratios after more like the situation described above

Next. replace the entire res after this point.

if this isn’t what you’re doing, or you’re topping off the evap water with more nutrient solution, and you have any problems with your plants. It’s your fault. Not the nutrients, res, or plants being pick....it’s you being lazy or cheap and not taking adequate care of your plant health lol.


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## kmog33 (Jan 10, 2020)

Aqua Man said:


> I'm keeping it simple here but I also do the same. Readings before and after add backs.


I never take readings at all, I don’t ph water, single part nutrient mix, etc. I very rarely have problems because I give my plants fresh shit all the time. I’m not trying to balance ratios of nutrients, they do the work for me if you keep fresh solution in maybe once a month.


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> You don’t top off with new nutrient solution. That’s fucking dumb. You’re intentionally throwing your mix off balance hoping the plant hasn’t totally destroyed one part in your older solutions because you will end up crazy imbalanced or tox, even at low ec/ppm.
> 
> The right way:
> 
> ...


Just gonna call it the way I see it.... BS. If you have significant or measurable evaporation your doing it wrong. The nutrient ratios used to grow can vary greatly with almost identical results. The change in ratios over time is directly related to the size of the system and nutrient uptake. 

Are you seriously saying if you have a 100gal system for one plant you need to be changing it after 1-2 top up because of nutrient ratios... Gtfoh it's dependant on the system volume and a res change after adding back equal to the system is absolutely adequate and you absolutely wrong if you think otherwise. Nutrient ratios can vary greatly hell some grow with 1-1-1 some 2-1-3 etc etc. Give your head a shake if you think they will change that much in adding back the volume of the system before changing.

Excuse me for being harsh but you stormed in screaming facts that are absolutely bullshit


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> I never take readings at all, I don’t ph water, single part nutrient mix, etc. I very rarely have problems because I give my plants fresh shit all the time. I’m not trying to balance ratios of nutrients, they do the work for me if you keep fresh solution in maybe once a month.


What's your point? You can half assed lots of things that work. I'm talking about keeping things as dialed in as possible. I never said you can't half ass it and grow plants.

Also the slower your plants grow the more forgiving it is so who knows maybe your system is not nearly as effective? Idk but the faster a plant grows the more dialed in you need the environment.


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## kmog33 (Jan 10, 2020)

Aqua Man said:


> What's your point? You can half assed lots of things that work. I'm talking about keeping things as dialed in as possible. I never said you can't half ass it and grow plants.
> 
> Also the slower you plants go the more forgiving it is so who knows maybe your system is not nearly as effective? Idk but the faster a plant grows the more dialed in you need the environment.


If you want to keep it dialed for dtw or replace your nutrient solution every day.
Adding nutrient solution to top off solution has a higher chance of negatively affecting the plant than making them grow faster.


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> If you want to keep it dialed for dtw or replace your nutrient solution every day.
> Adding nutrient solution to top off solution has a higher chance of negatively affecting the plant than making them grow faster.


Lmao why are you talking DTW? Why the hell would you come into this and compare DTW and RDWC? Smh


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## kmog33 (Jan 10, 2020)

sandman83 said:


> This might be the confusion, if you are talking DTW and he is planning for recirculating.


The second part then. Change it every day if you want true dialed system. Outside of this situation you’ll always be less than optimal as the plants feed constantly. Going to see the effect faster with older hungrier plants.


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## kmog33 (Jan 10, 2020)

Because you’re debating about running a dialed system. Not an rdwc


Aqua Man said:


> Lmao why are you talking DTW? Why the hell would you come into this and compare DTW and RDWC? Smh


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> The second part then. Change it every day if you want true dialed system. Outside of this situation you’ll always be less than optimal as the plants feed constantly. Going to see the effect faster with older hungrier plants.


Just fucking clueless... You have anything to back up what your saying? I have a feeling your either trolling or just looking to argue and look stupid


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> Because you’re debating about running a dialed system. Not an rdwc


It's pretty dam obvious... Did you even read the thread or just roll in here like captain America to save the day?


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## kmog33 (Jan 10, 2020)

Aqua Man said:


> Just fucking clueless... You have anything to back up what your saying? I have a feeling your either trolling or just looking to argue and look stupid


Lol, you’re a funny guy. Care to come up with a legit argument to any of my point?


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## kmog33 (Jan 10, 2020)

Aqua Man said:


> It's pretty dam obvious... Did you even read the thread or just roll in here like captain America to save the day?


I’m betting you’re the one that revived this old ass thread?


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> I’m betting you’re the one that revived this old ass thread?


I'm betting you have a habit of being totally wrong... Scroll back.


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## Aqua Man (Jan 10, 2020)

One day we will remove the warning labels and let the world sort itself out for the benefit of mankind.


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## kmog33 (Jan 10, 2020)

Aqua Man said:


> I'm betting you have a habit of being totally wrong... Scroll back.


lol you really want to change the focus from optimal res top off to an argument...nice bud.

read my first post on here, trolling because I think you guys are dumb for reviving an old ass thread to debate on info that very easily available.


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## Wastei (Jan 10, 2020)

I add back 1/8 strength or 12.5% mid week. EC remains the same in my 14 gallon reservoir.


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## Aqua Man (Jan 10, 2020)

Wastei said:


> I add back 1/8 strength or 12.5% mid week. EC remains the same in my 14 gallon reservoir.


Yep no hard fast rule I prefer 33% as goal but with everyone's systems a bit different well all need to adjust to ours. The principal stays the same.


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## Aqua Man (Jan 10, 2020)

kmog33 said:


> lol you really want to change the focus from optimal res top off to an argument...nice bud.
> 
> read my first post on here, trolling because I think you guys are dumb for reviving an old ass thread to debate on info that very easily available.


No debate someone had a question they asking in an old thread with relevant info to the question they had Mr. Hall monitor. Kinda the purpose of a forum. Funny things is how offended you are by someone else's questions.


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## Keesje (Jan 10, 2020)

Aqua Man said:


> Ok so you have a 40 gal res and say daily you plants are drinking 10gal. Your EC is 1.2.
> 
> You mix up 10 gal with 33% concentration. 0.4 add it back to the res. Your EC is 1.2 after add back.. your perfect.


How is this possible?
If I have 30 gallons in my res with an EC of 1.2 and I add 10 gallons with an EC of 0.4, how can the new EC then also be 1.2 ?



kmog33 said:


> You don’t top off with new nutrient solution. That’s fucking dumb. You’re intentionally throwing your mix off balance hoping the plant hasn’t totally destroyed one part in your older solutions because you will end up crazy imbalanced or tox, even at low ec/ppm.


In a recurculating system the solution is already off balance after the first time you water your plants.
So if you add water with an EC of 0.0 or water with an EC of O.4 will not solve the problem of imbalance.
The only difference will be that top off with an EC of 0.0 or top off with water with an EC of O.4 will be that the ratio of single nutrients will be different between the 2. But us growers can not tell which one is the better solution after topping off.
For that you would need other equipment.


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## Aqua Man (Jan 10, 2020)

Keesje said:


> How is this possible?
> If I have 30 gallons in my res with an EC of 1.2 and I add 10 gallons with an EC of 0.4, how can the new EC then also be 1.2 ?
> 
> 
> ...


Ok your full res is EC 1.2 the plants drink 10 gal and as such ideally that concentration is going to increase as the plants are drinking slight more water than taking up food so the EC increases as the plants drink... Say 1.3 now after they drink 10 gal. You add back a solution of 33% the EC drops back to 1.2 and you are pretty close to where ya wanna be.

Like at @Wastei it depends on the strain some feed more than others and I prefer 33% add back to achieve the starting ppm. After doing it a for a bit you will find a number that works best for your conditions and strains.

I suggest starting at 33% as a target. So if ya add back 33% and end up with the same EC observe the plants if all is good stick to that.

If EC after add back is lower than originally then you need to bump the overall ppm up. I suggest no more than 20% at a time so I may increase the res EC to 1.4 and add back 33% of 1.4 to dial it in

If the EC is higher than originally then you need to lower the overall ppm. I may drop to EC of 1.0 and add back 33% of that to dial it in.

Again it's a guideline and will take some practice but pays dividends in understanding you plants nutrient needs and all but eliminates nutrient issues.

It's just allows you to really understand the plants nutrient uptake and dial right in you feeding. If you have adequate nutrient ratios to start with you will eliminate any and all toxicity or deficiency issues by giving the plant exactly what it's asking for.


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## Aqua Man (Jan 10, 2020)

It gives you so much info you can see the cycles of how the plant increases and slows nutrient uptake. You can see if anything is going wrong with respiration or roots almost immediately before visable signs based on ppm changes and water uptake... I mean it just provides so many answers and assurances. It is more work but the info gained is irreplaceable


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## Keesje (Jan 10, 2020)

Aqua Man said:


> Ok your full res is EC 1.2 the plants drink 10 gal and as such ideally that concentration is going to increase as the plants are drinking slight more water than taking up food so the EC increases as the plants drink... Say 1.3 now after they drink 10 gal. You add back a solution of 33% the EC drops back to 1.2 and you are pretty close to where ya wanna be.


Now I do understand your point of view and method. Thanks!


I visit a hydro greenhouse in my area now and then.
They can measure single elements in their (huge) reservoir.
So they do top off with water like we do, but they add single elements to get to the perfect balance of elements every day.

The big problem that we face (in recirculating systems) is that after just 1 feed, there is already an imbalance. And the imbalance will get bigger and bigger by the day. Just because roots absorb different elements at different quantities.
By topping of with RO water your imbalance will not disappear. Also you risk that your EC will go down.
By topping of with a 33%, 50% or 100% solution the imbalance will also not disappear. And the risk that your EC will get to high.
If 'repairing' the imbalance is your main goal, then there is no proof what will work better. The only proof that one could get, if you could measure every single element or send your water to a laboratory every day.
Perhaps there is a grower here that has the financial means to do this


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## Aqua Man (Jan 10, 2020)

Keesje said:


> Now I do understand your point of view and method. Thanks!
> 
> 
> I visit a hydro greenhouse in my area now and then.
> ...


Much agreed that's why after adding back the volume of the system you change the water. This has been time tested and proven to work. Without adding back anything the ratio will change faster.

To give a simple example of why this works. If you look at planted tank aquariums most used what's called the EI (estimated index) method developed by Tom Barr. I won't get into all the shit as it's a never-ending topic much like hydro. They do 50% water changes weekly and replace the water with nutrients at 100% concentration. So what this does is limit how far the nutrient imbalance can get. You can google it and look at the math behind it rather than my lazy ass try to type it out. But basically by doing this weekly you can be guaranteed that you ratios stay withing in a certain percentage. The reason being for 50% is the preservation of bacterial populations. Now this is kind of how I do my system. I never change more than 50% of my water for the same reasons but I won't get into that. I have over 20years breeding fish and aquatic plants and testing specific nutrient levels much like the greenhouses you talk about but not quite on that level, so I have incorporated quite a bit of that into my system.

What I'm trying to say is that if you do a res change after adding back the volume of your system the nutrient ratios will not change enough to impact the plants.


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## Aqua Man (Jan 10, 2020)

Keesje said:


> Now I do understand your point of view and method. Thanks!
> 
> 
> I visit a hydro greenhouse in my area now and then.
> ...


The amount of change a day will be directly related to the volume of the solution and the amount of uptake. So while it does change daily the amount of change differs based on those factors.

Also I would look at it as a small change in ratios as an imbalance would suggest the ratios are no longer adequate. If we look around we can see a large variety of ratios work.


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## Keesje (Jan 10, 2020)

True.

The reply was more meant for people who claim that their system is the one and only right way.


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## Aqua Man (Jan 10, 2020)

Keesje said:


> True.
> 
> The reply was more meant for people who claim that their system is the one and only right way.


Absolutely in growing there is generally never one right answer nor solution. 

Eg. Changing nutrients every week also can work.


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## SuperiorBuds (Jan 10, 2020)

Keesje said:


> What you call a 'side-effect' of the Torus Hydro (keeping the pH in check) is the main purpose of such a device, as I understand from their website.
> In what way do you think it helps the EC of the nutrient as well?


Perhaps that wasn't worded clearly. I never said it did anything to the EC. I understand that keeping the pH in check is what it's meant for -- it's literally why I have it.

The side-effect is that because it's using ion-exchange instead of adding an acid or a base to the solution you can now keep the reservoir longer w/o dumping it. If you're adding pH up or down you NEED to flush the reservoir every week (or two at most) to get things back to neutral before you adjust.


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## SnidleyBluntash (Jan 10, 2020)

Trial and error. If your pH is at 6.8 and you want to get it back to 5.8, just make a more concentrated top up solution. Once you do it so many times you will know how many squirts it takes change the pH. 
Same thing with ppm. If you want to lower the ppm, use plain water.


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## 5BY5LEC (Jan 10, 2020)

Sorry if this has been said, but you are totally over complicating it.
Listen, get a one gallon jug and mix up a strong nutrient solution using the same ratio you normally use.
Fill your system up with water, then use the nutrient jug solution to get your PPM back to where you want. Adjust PH. Done.
Once you have added back the total volume of your system, change the water.


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## Keesje (Jan 11, 2020)

You call some methods too complicated, and perhaps you are right.
But I am sorry to say that I do not understand your explanation as well



5BY5LEC said:


> Listen, get a one gallon jug and mix up a strong nutrient solution using the same ratio you normally use.


What is a 'strong nutrient solution' when you say at the same time 'using the same ratio as you normally do'?
Strong for example is an ec of 2.4, but if my ratio normally is getting an EC of 1.0... what to do?
Or do you mean: Get a gallon jug, put in a gallon of water and mix in it the amount of nutrients that you normally would mix in your whole reservoir?
Or the amount of nutrients that you would need for the amount of water that is needed for the top off?
Perhaps you mean even something else?



5BY5LEC said:


> Fill your system up with water, then use the nutrient jug solution to get your PPM back to where you want. Adjust PH. Done.


Why this extra step of the 'jug solution'?
Why not top your system off with water, and add nutrients until you get the PPM to where you want?

I am here to learn, so all info is welcome.


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## Keesje (Jan 11, 2020)

SnidleyBluntash said:


> Trial and error. If your pH is at 6.8 and you want to get it back to 5.8, just make a more concentrated top up solution. Once you do it so many times you will know how many squirts it takes change the pH.


Perhaps this works with your water and circumstances, but I am not sure if it will work in all situations.
pH is depending on several factors, not only the concentration of a solution.
Or did I misunderstand?

And if I add with a more concentrated top off, then there might be a chance that the EC will get too high.
How to avoid that with your method?


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## Aqua Man (Jan 11, 2020)

5BY5LEC said:


> Sorry if this has been said, but you are totally over complicating it.
> Listen, get a one gallon jug and mix up a strong nutrient solution using the same ratio you normally use.
> Fill your system up with water, then use the nutrient jug solution to get your PPM back to where you want. Adjust PH. Done.
> Once you have added back the total volume of your system, change the water.


That's definitely easier but provides little to no info about the plants needs. Unless your gonna sit down and do the math but then you are just doing what I am a different way. 

Im not saying the way I explained is the only or right way. It just provides some benefits that I feel can really help a grower understand the plants needs much better. It is more work but provides a window into the changes of your plants needs. Of course we can make it as simple or complex as we want I was just providing an option for those looking to up thier game


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## fragileassassin (Jan 11, 2020)

I have a barrel that feeds into a float valve in my outside control res. I mix the barrel at the same strength as the system. 55 gallon barrel to a roughly 65 gallon system. When the barrel is empty, I let it run for a few days to see if anything goes up or down then do a 90% change and repeat.


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## 5BY5LEC (Jan 12, 2020)

Maybe it would have been better worded as "There are a lot of ways to add back, but none have to be complicated".
Keesje, let me explain. LOL I call strong solution 1.0EC or 500ppm.
So in my case I run 20 gallons. At this point I use (ml) 20 Calmag/ 20 Micro/40 bloom for that entire 20 gallons to get me to around 400ppm.(.8EC) A general "week 7 flower" mix.
So in a one gallon jug I would use that same ratio just maybe less, in other words I would use 10/10/20 for that one gallon jug.
I mix said jug up and keep it next to my res, or in the fridge if it is summertime. I add water to the res, and then use the one gallon jug with the "hot mix" to get the PPM back up, since ppm will have dropped with adding water.


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## 5BY5LEC (Jan 12, 2020)

fragileassassin said:


> I have a barrel that feeds into a float valve in my outside control res. I mix the barrel at the same strength as the system. 55 gallon barrel to a roughly 65 gallon system. When the barrel is empty, I let it run for a few days to see if anything goes up or down then do a 90% change and repeat.


This would actually be the best way to do it. Have the top off hold whatever the maximum amount of water the plants will use until next res change.
Literally mix the top off and let IT do the work keeping your stuff in check during the week.


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## SnidleyBluntash (Jan 12, 2020)

fragileassassin said:


> I have a barrel that feeds into a float valve in my outside control res. I mix the barrel at the same strength as the system. 55 gallon barrel to a roughly 65 gallon system. When the barrel is empty, I let it run for a few days to see if anything goes up or down then do a 90% change and repeat


 do you worry about the external rez “going bad” over time? Some claims say to use the product right away after being made and not let them sit. I imagine some living organism products this could matter for, and maybe some chemical reactions occurs to reach equilibrium, but would just nute salts ‘go bad’ in solution? I don’t think so.


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## fragileassassin (Jan 12, 2020)

SnidleyBluntash said:


> do you worry about the external rez “going bad” over time? Some claims say to use the product right away after being made and not let them sit. I imagine some living organism products this could matter for, and maybe some chemical reactions occurs to reach equilibrium, but would just nute salts ‘go bad’ in solution? I don’t think so.


I use megacrop, they said you can mix and store it for a pretty long time. I dont remember how long it was, but wayy longer than it sits for me, and this is one of the reasons I use it. I have a pump in the barrel on a timer that pumps it up to the top to mix it for 15 mins every few hours. I add my southern ag fungicide to it just like I do the system. Painted the barrel so no light gets in it and it sits on 2 concrete blocks on the basement floor and that keeps it cool enough.
I just cut the system in half. It was previously 12 sites and around 130 gallons total. It emptied a full 55 gallon barrel as fast as 4 days. At that rate I'd run 3-4 barrels between changes.


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## Dro3420 (Jan 14, 2020)

endogarden said:


> Sorry if this has been gone over, if so please direct me to the information! I am having some trouble wrapping my head around the concept of refilling a reservoir that still has nutrient solution in it. I'm specifically referring to flood/drain ebb/flow, but any recirculating rez would apply.
> 
> Let's say for example (I made these numbers up from recent experience), I add 20 gal of RO water @ 6.8pH and 10ppm, I add 5ml per gal of MagiCal, bringing the ppm to 260. Then I add veg nutes, upping the water to 850ppm. The pH has now gone down to like 4.5pH, so I add pH Up til it's at 5.6pH, the water is now 900ppm. I feed the ladies, afterwards the rez is low, they were thirsty.
> 
> ...


There is no way to tell precisely how much of what nutrient is left.


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## Dro3420 (Jan 14, 2020)

Dro3420 said:


> There is no way to tell precisely how much of what nutrient is left.


U just add what ur missing. If 1/4 of ur rez in empty add 1/4 water with 1/4 strength nutes. Then every 7 to 10 days change out completely


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## Dustuballz (Apr 15, 2020)

If my ec reeding is going up I add plain ph water if my ec level is staying the same as the water level drops this I let the plants drink until the next res change I change my res every 2 weeks and it's a 55 gallon tank.


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## fartoblue (Apr 16, 2020)

I haven't read all of the posts on this thread but here's my twopeneth. I had some great advice from "Dr. Who" a few months ago. I have followed this advice and tweaked it to my own setup and plants, so far this seems to be working fine. Everything looks healthy and happy.

I have 2 x 200 litre rez grows, each has a 200 litre top up tank gravity fed through a float valve (ballcock).

I fill my rez up with everything I want in there to 1.6 ec and 5.8 to 6.2 PH (if it is within this PH range I don't adjust it). I am 2.5 weeks into flower.
I then fill my 200 litre top up tanks with tap water (in my case it is zero - 0.2 ec straight from the faucet 7.2 PH), firstly I add cal.mag to 0.5 - 0.6 ec, I then add nutrients to just over 1/2 the rez strength (somewhere around 0.9 - 1.0 ec in my case @ 2.5 weeks into flower). If it is under 6.5 PH (in the storage tanks) I don't adjust it

As soon as the 200 litre storage tank has been used up or in 2 weeks time whichever comes first I do a rez change and do just the same again until I am in the last few weeks when I only add water and cal/mag to the storage tank (in other words as soon as the rez has used up its volume in added nutrient solution or in 2 weeks time I change out). I don't add any boosters or anything to my storage tanks just nutes, I do put additives into the main rez at every res change. When I res change I flush the system with clean water to remove the residual old nutrients and test the ec until it is 0.2 before I refill the rez.

I adjust the nute strength in the res itself. With this technique (in my setup) my rez strength seems to stay stable or drops slightly every few days.

I run top feed 60/40 coco/clay in 20 litre pots recirculated (24/7 recirculating pump water falling back into main res). My storage tanks are also recirculated 24/7 with a small pump from bottom of tank to top and water falling back just to keep them fresh. I DO NOT have any air stones anywhere.

This works well for my setup but if your roots are in the main rez water then it may be more complicated adding nutes directly to the main res you may be better off adjusting the storage tank which IMO would take to long to get into the system. I suppose you could add it to the main rez very slowly. The flushing of the system before a refill would also probably cause problems (this (and root rot) is why I will never put roots into a rez ever again, I know it works for some but for me RDWC roots in res was a nightmare for over a year)

This is just how I have started to do it and it works for me and my setup, not telling people how it should be done as I don't have the experience to advise anyone (only been growing around 3 years).


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## RCJR (Feb 3, 2021)

Aqua Man said:


> Ok your full res is EC 1.2 the plants drink 10 gal and as such ideally that concentration is going to increase as the plants are drinking slight more water than taking up food so the EC increases as the plants drink... Say 1.3 now after they drink 10 gal. You add back a solution of 33% the EC drops back to 1.2 and you are pretty close to where ya wanna be.
> 
> Like at @Wastei it depends on the strain some feed more than others and I prefer 33% add back to achieve the starting ppm. After doing it a for a bit you will find a number that works best for your conditions and strains.
> 
> ...


Sorry I'm late to the party but i do have a question for you aqua;
You guys where referencing a 40 gallon res with 10 gallons missing for the 33% add back solution to work. Does this 33% math only work when 25% of the water in the res is missing? Say i have a 20 gallon res (my target ec is 1.2) and 2 gallons was uptaken by the plant overnight (the ec stayed the same at 1.2) Could i add 2 gallons of the 33% of the target ec (which would be 2 gallons at .4 ec) back and the math would still work?


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## RCJR (Feb 3, 2021)

so i made myself this chart to follow. Is this correct with your method?

*20 gallon RDWC res*

20 gallon res change with fresh water and nutes to the desired EC range (1.2 EC at ph of 5.

Wait a day or 2 until the water level drops (ideally the EC should be 1.2 or 1.3 at this point)

Make a 33% solution (.4 EC) in separate container and add back until the res is full again (i don't have a way to see exactly how many gallons the res is low so ill make more than what i think it will take)

Once the res is topped off with this 33% solution and the EC is at the target range of 1.2 (at 5.. Your nutes are dialed in.

If the EC is higher than 1.2 (at 5. after the 33% top off your target EC needs to be lower

If the EC is lower than 1.2 (at 5. after the 33% top off your target EC needs to be higher

Don't increase or decrease more than 20%at a time

After you have filled the system with 20 gallons of top off solution it's time for a complete res change​


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## RCJR (Feb 3, 2021)

RCJR said:


> so i made myself this chart to follow. Is this correct with your method?
> 
> *20 gallon RDWC res*
> 
> ...


i have no idea why the number 8 is an emoji? but the faces are supposed to be a number 8


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