Can you run a recirculating reservoir for 2 weeks...?

firsttimeARE said:

MJ needs change throughout the grow cycle. Which is why feeding schedules have you varying the amounts

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Especially with hydro

Chumly said:

Don't mean to hijack the op's thread but as a noobie wasn't sure where to get help getting a definitive answer to this. What exactly does a rising or falling ec and ph levels mean. From what reading I've done, mostly from internet sites like these, I can't seem to get a definite answer, hope someone here can help.
1.A rising ec and a falling ph means the Rez is too hot and there's too strong of a solution for the plants and are consuming more water than nutes, thus making the solution more concentrated.
2. A falling ec and a rising ph indicates the Rez is too weak and is consuming more nutes than water thus reducing the concentration of the rez solution.
3. A relatively stable ec and ph indicates that the rez is pretty much at the proper concentration and is at proper equilibrium and is pretty much at the happy medium for the plants.
I am not sure where I came up with this thought of thinking, but remember reading it on a few different sources from around the net. My question to all you experienced growers out there, is this train of thought right? Any help would be greatly appreciated to help clarifying this with me. Thanks!!

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In my experience an optimum reservoir will slightly raise in both ph and ec due to the almost equal uptake of water and nutrients (slightly faster water uptake) and the Chemical secretions of the root mass.

In flower we’re purposely utilising a vpd where the water is drawn off the plant via the atmosphere due to lower humidity. Therefor the water is used quicker than the minerals which in turn increases ec in the res.

Like I said I ain’t got paper proof, just experience. A healthy efficient functioning pathogen free oxygenated res should always be climbing in ph and ec

Blue brother said:

In my experience an optimum reservoir will slightly raise in both ph and ec due to the almost equal uptake of water and nutrients (slightly faster water uptake) and the Chemical secretions of the root mass.

In flower we’re purposely utilising a vpd where the water is drawn off the plant via the atmosphere due to lower humidity. Therefor the water is used quicker than the minerals which in turn increases ec in the res.

Like I said I ain’t got paper proof, just experience. A healthy efficient functioning pathogen free oxygenated res should always be climbing in ph and ec

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I was thinking it might have to do with the evaporation of the water, leaving salts behind, thus raising the TDS, and messing with the pH. That was just a theory though.

I found that I like to leave my DWC at 55-gallons, because it really stays stable. I lower it a little towards the end, to save on nutes, but I can go a month or more if I stretched it, without a flush. Everything stays stable, and I just add a spoon or cup of nutes each day, respective to what week I'm in. It got to the point where I'd go a while without checking my TDS, because my plants were always looking nice and healthy.

Twerkle said:

if your ec is going up that means u are over feeding. EC should stay the same if your plants are drink water and nutes at equal levels or drop if they are drinking more nutes than water. Its common sense lol. Also they should have a range, usually between 30 and 50% ec drop before change or every weak, which ever is sooner.

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Well when I say it slowly rises I really mean slowly lol. I feed in flower at 1.2 EC, if I go lower I start to have stability issues with PH and plants are quite happy. I spent about two years dialing the res in and with my water makeup things are going well. Your EC drops by an average of 40% over a week? What nutrients are you using?

Budley Doright said:

Well when I say it slowly rises I really mean slowly lol. I feed in flower at 1.2 EC, if I go lower I start to have stability issues with PH and plants are quite happy. I spent about two years dialing the res in and with my water makeup things are going well. Your EC drops by an average of 40% over a week? What nutrients are you using?

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GH Maxi

JSB99 said:

GH Maxi

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Cash crop shiva a+b is the best thing you sterile dwc guys will ever use, check it out. Amazing stuff

If I lower my EC to the point the it drops I'm down below an EC of 1. The plants seem much happier at a higher EC where it rises slowly. Yup I have tried to get it to the point of dropping and it just doesn't work in my setup for reasons I do not know lol.

Twerkle said:

if your ec is going up that means u are over feeding. EC should stay the same if your plants are drink water and nutes at equal levels or drop if they are drinking more nutes than water. Its common sense lol. Also they should have a range, usually between 30 and 50% ec drop before change or every weak, which ever is sooner.

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Common sense would then dictate my plants should show signs of burning and N toxicity if in fact what you say is true across the board? Sorry but I don't see this with my girls. If anything I'm thinking I could up my EC and still be ok but have not tried to max out the EC. I'm switching to seperate containers to do a bit of testing on my next run to see what differences occur with different EC levels.

JSB99 said:

I was thinking it might have to do with the evaporation of the water, leaving salts behind, thus raising the TDS, and messing with the pH. That was just a theory though.

I found that I like to leave my DWC at 55-gallons, because it really stays stable. I lower it a little towards the end, to save on nutes, but I can go a month or more if I stretched it, without a flush. Everything stays stable, and I just add a spoon or cup of nutes each day, respective to what week I'm in. It got to the point where I'd go a while without checking my TDS, because my plants were always looking nice and healthy.

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I do check EC but having never calibrated the meter I have no clue if it's a true reading. What I do watch is the movement of the readings over a period of time. It's more about reading the plant then meeting a certain level of nutrients for me. Your running 55 gallon DWC containers? Wow, big ones, I'm assuming your doing large plants?

In a lower than 50% rh environment and a constant temperature of 27.5’c water is lost to the atmosphere due to the vapour pressure deficit in the room. So the plant and the medium and the res for that matter will allways be losing water to the atmosphere. Maybe in a cold high humidity room you might see the ec stay stable for a long time but if you’re environment is optimum you’ll be using more water than nutrients, if your ppm is dropping ur not feeding optimum amounts of nutrients and the plants are using the nutes quicker than the water

Budley Doright said:

I do check EC but having never calibrated the meter I have no clue if it's a true reading. What I do watch is the movement of the readings over a period of time. It's more about reading the plant then meeting a certain level of nutrients for me. Your running 55 gallon DWC containers? Wow, big ones, I'm assuming your doing large plants?

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LOL! Not 55-gallon totes. They are the 27-gallon totes, although I do have a 55-gallon tote I use for a reservoir.

JSB99 said:

LOL! Not 55-gallon totes. They are the 27-gallon totes, although I do have a 55-gallon tote I use for a reservoir.

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Opps thought I read 55 gallon DWC containers . I run 22 gallon totes but run 4 to 6 plants in an upper tote that has another 5 gallon capacity if running recirc.

nxsov180db said:

What EC do you normally feed at?

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1.2ish in the throws of flower but when I was doing LPS I had to up that to 1.6ish to keep plants happy. I also start at 5.6-.7 ph and it will slowly climb to 6.1-.2 when I change out res. if it starts to drop I also do a change out.

Like just about everyone has said I usually go 3ish weeks before change. I top off with ph'd water in early veg and flower and in the heat of both I'll top off with nutrients if the ppm dips by 300 or more in between changes. Sometimes I have time and do it a little earlier. Sometimes I'm lazy or busy and do it after 4 ish weeks. It's all about your system and what works for you. And what you can afford. With AN or even gh 3 part hell no I couldn't afford a res a week. With megacrop maybe I could but I'm not going to. Especially since my system runs 300 gph in water flow and 2 airstones per site with 3 in the res. Lots of movement and mixing.

nxsov180db said:

I've also had both my ph rise as well as my EC. I wonder if we are feeding too much of one thing and not enough of the other? Like maybe our plants are P hungry and leaving behind N because they don't want as much so your EC goes up as well as PH but they are still hungry? idk just a theory..

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Possibly, I'm sure that I have read in the past that EC rising may not mean you are under feeding but I do forget the content, it may have been linked to the Lucas formula. If my girls showed any issues then I would be concerned but they seem happy.

Budley Doright said:

Possibly, I'm sure that I have read in the past that EC rising may not mean you are under feeding but I do forget the content, it may have been linked to the Lucas formula. If my girls showed any issues then I would be concerned but they seem happy.

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I think the slight increase in ec just means there is a little bit of water evaporation or you're feeding just slightly too much. If you use high quality ferts with little ammonia based nitrogen you may not notice tip burn or curling at a slightly high ec. Or perhaps yes you are leaving behind some of the less soluble heavy salts.

Cold$moke said:

If i recall the direct absorbtion of nitrogen
Is directly related to the uptake of other nutrients
Iron being one if i recall there are about 2 more that also directly affect nitrogen uptake

Per harvey smith look up his vids he can explain it better than i

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Thats who I was paraphrasing actually. I love harvey and use a lot of NPKs products. N is a luxury to the plant so it will consume it all. He even says thats why ppl think flushing is a thing, because they run water through the pot and it washes out N first cause its the most easily removed from the medium then their plants yellow becuase they think its using its stored energy when really its canablizing itself cause u washed the N out.

nxsov180db said:

@im4satori what are your thoughts on this?

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well theres more than one way to get the job done I suppose

I have my way, theres lots of people who feed amounts I would consider insane and seem to do all right

EC1.2 isn't high at all and not something I would be overly concerned with

either, your going to lower your EC to get the ph rise and slight Ec drop or your going to make a habit of flushing your medium (if you have medium) on occasion as the salts accumulate

at an EC of 1.2 if there was a salt accumulation it would be slow and not enough to cause leaf tip curl or signs of over fertilization

some people might like to push there plants a little more I suppose, but as long as the medium salinity doesn't eventually climb to high levels before being flushed im sure itll all work out fine

if your in a DWC and changing the reservoir on the regular its likely fine provided your topping off and reducing the EC again before it reaches critical levels

lastly
you could consider, the excess P in your lucas fertilizer mix could be left behind in the solution if the plant cant use it all at the higher levels and that could be part of the reason for increase....

and another potential could be the low N ratio in the lucas formula.... sometimes people using the lucas formula will feed higher EC to meet the N requirements of the plant where as a nutrient ratio with a higher proportion of N could allow for a lower EC solution

so its possible your plants would prefer a slightly different nutrient ratio

but
that's all speculation or food for thought

if your happy and your plants are happy then im happy

as far as evaporation of the water content in your reservoir

try this

fill a 5 gallon bucket up with water

wait a week and see how much water has gone....im betting its not enough to affect a 55 gallon reservoir EC by more than a tiny fraction

Keeping in mind that again when I say rise in EC I'm talking .1or .2 over a period of a week or more depending on stage. This is all in a recirculating or ebb and flow setup with no media (the topic of the thread). As I have stated, the plants seem happy and if I drop the EC my girls will show it by general lightening of leaves slightly. As I have found with many discussions here there seems to be no consensus on pretty much anything, which leads me to believe that each setup has its own unique requirements. More importantly then, IMO, it is better to start with the basic concepts and tweak to the needs of your particular setup. I'm still tweaking and fear that will never end lol.

Cold$moke said:

If i recall the direct absorbtion of nitrogen
Is directly related to the uptake of other nutrients
Iron being one if i recall there are about 2 more that also directly affect nitrogen uptake

Per harvey smith look up his vids he can explain it better than i

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Thanks, some great stuff!