How much should a stable PPM fluctuate?

So I'm familiar with the concept that I should check my PPM after topping off the res, note the level and then tomorrow before topping off again I check the PPM. If the PPM has risen I need to lower the PPM from where it was last night, if it's fallen I need to raise the PPM from what it was last night.

Here's the question what buffer do you use to decide if it went up or down. For example if the PPM dropped from 500 to 490 over 24 hours do you consider that a drop in PPM or is that stable? what about a drop of 30 PPM, 50 PPM, etc. At what point to do consider the PPM to be rising or falling?

Whenever it rises or falls is when its rising or falling. And when its stable...well its stable.

I like to see a small drop each day.

Mine will go from 500 to 200 in a week. I like to see them eating. If I was more OCD I would readjust them when they went down 150 ppm or so.

70's natureboy said:

Mine will go from 500 to 200 in a week. I like to see them eating. If I was more OCD I would readjust them when they went down 150 ppm or so.

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So you don't top up your water, you just let it run down all week?

Mine will be 500 tonight, tomorrow I'll come in and it will have drank 3/4 of a gallon of water and the PPM has risen to 600. I add 3/4 of a gallon of water, the PPM is now 450, since 500 was too high I'll leave it at 450 tonight. Tomorrow I come in it's drank the same amount of water and the PPM has risen to 525, so now I drop it to 400 PPM. This continues and after a couple weeks I'm at 250 PPM on a healthy plant on week 5 of flower and it's still telling me that's too strong and I'm getting worried about what's wrong that the PPM keeps climbing every day even though i drop it lower and lower every night. It's to the point now that my plants in week 5 of flower are using lower PPM than they did during veg

It should not "should" anything. PPM fluctuations are from a difference between water uptake and nutrient uptake amd does not tell you whether the plants need more or less nutrients and means little to nothing by itself. That concept you are familiar with is often referred to as finding the sweetspot, which is essentially just forum nonsense. Instead, run 1.0 EC / 500 ppm and look at the plants (darkness and light tips) and they will let you know if they need more or less. The concentration obviously depends heavily on the amount of water. What matters is the amount of nutrients the plant takes up, the amount in ml you use per week or cycle.

wow my feeding chart (fox farms) says i should keep my ppm around 1200 to 1700 thru flowering

They probably tell you to use 7 different bottles too. Run 1.0 ec,give or take 0.2, of base nutes only, from start to finish just once and you'll never look back.

Anything that's stable doesn't fluctuate..a drop in PPM is a drop..the plants ate something..but i digress..

I'm just getting my head wrapped around this stuff..

I make adjustments to keep my EC within a range of a .1 +/- . A measurement of .1 ec is equal to [email protected] or [email protected]., so i don't let it drift more than say 50 ppm. Let's say you start with 20L@500ppm and the next day they drank 2L and the PPM is up to 550, so you dilute back down to 500ppm. Next day same thing..drank 2L, up to 550ppm. Now you dilute down to 450PPM this time...next day they drank 2L again but now PPM is at 470..so you would dilute down to 420..next day drank 2L..still at 420..do nothing..next day drank 2L, 420...you now have a stable res for that stage of growth of that strain. Nute strengths will vary by plant stage,size and strain so this is a process that needs to be gone thru with each new strain through all the stages, if you want to fully optimize results. It's why many people stick with one strain for a few grows, so they can really dial it in.

My PPM goes up and down small increments all week(might be my cheap PPM reader for why I see it go up a little, idk)mostly it slowly goes down, really doesn't mean anything to me on a day by day basis though. The only thing I use PPM for is to know by an overall timeline basis, basically I start with 100 at seedling, by week 3 I know it'll generally be hungry to start at 500ppm and at the highest for my last plant in a 5 gal bucket I've gone to about 1200ppm in heavy flower. I never put nutes in the same water twice, beginning of week I fill the bucket with new water and nutes, let it drink it down and restart fresh next week, fill bucket with new water and nutes. Overall, like Weedfreak said, it all depends on a buncha dif shit so no one can really compare unless you're doing 100% the exact same thing.

My last crop the ppm was raising even as low as .8EC(400ppm on my meter) in mid flower.

I could never find that "sweet spot." I concluded that my plants were just drinking a lot as the temps were mid to high 80s.

Im beginning to feel the same as sativied. Use a low feed and pay attention to signs of over or underfeeding.

firsttimeARE said:

Im beginning to feel the same as sativied. Use a low feed and pay attention to signs of over or underfeeding.

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^right here..you can under feed a plant leaving room to add more nutes if you think it needs it and still get an excellent crop of top notch bud. Once you start overfeeding there's not much you can do but stop feeding until it recovers and still possibly be left with a plant full of damaged unproductive vegetation which need to recover and heal. You ideally want to use the least amount of ferts that will give you healthy growth, too little and the plants have deficiencies, slow growth and possible disease problems, too much and they can lockout nutrients, stunt/slow growth,effect the taste of the finished product and cost more $$$$

Finding that "sweet spot" isn't easy seeing how cannabis, in general, will grow well in a wide range, generally from 1.0-2. EC(strain/environment dependent). Where a certain strain might grow well within a smaller range(IE 1.2-1.7EC) but grow optimally at a 1.3EC. Finding the 1.5EC middle point would be fairly easy..chasing down that last final tweak could take a few grows. And just to throw some confusion in you should look at BASE nute EC separately from total nute EC and come up with a formula for that. I know how my additives/extras effect ec when mixed at their recommended dosages, because i have mixed them all separately and logged the data, so i adjust my base nute EC strength to accommodate the additives in order to get my final EC.

Example..I know my B vitamin adds .2EC, my bud booster adds .2EC, my K boost adds .2EC..so if i want a total of 2.0EC i would shot for a base mix of 1.4EC and the additives would bring it up another .6EC.

Some people will argue to mix base nutes full strength, because in all actuality you should only need a base nute with no additives, and adjust the additives to get final EC..either way can work..either way you need to be able to read plants.

Once i started to get a grasp of these concepts my plants became much more healthy and vigorous, because i wasn't nuking them with ferts ( never follow bottle instructions) as well as the side benefit of cutting my nutrient cost by almost 40% due to much lower usage.

My definition of a stable res/system is one that gradually declines in PPM as the PH increases.

Its funny, cause I find myself leaning towards following recommended mix ratios. I find...with the brand I use...if i mix below 50% recommended strength, the solution is not as stable..meaning it doesn't react predictably like it does at close to recommended strength.

At this point I'm not worrying about what my PPM is from day to day. I'm more concerned about it's overall trend over a few days to a week. The plants seem much happier but I'm not really sure if I'm finding a sweet spot or just somewhere in the ball park. My PPM flucuates around 50-100 per day now it seems. Although after diluting it by refilling the water it's usually about the same as it was the night before.

Hi. 1500 ppm. When i checked it was down to 1400 ppm, water level has dropped, so i topped the water up, ec was at 1300 ppm. Then i added premixed nutes to get rid of them and a few extra squirts of bloom since at this stage it is mostly using phosphor. Ppm back to 1500, ph at 5.8.

I do this every single day, 5-10 minutes in the morning makes all the difference in the world. If i notice ph at 6.3 or so, i toss in 1 cap full of ph down to the 105l bin it grows in. Just hit your targets and you'll do ok. Get used to different phases... right around stretch phase the plant seems to dramatically reduce it's use of ppm's and just drink mad water, ec went to 2000 ppm before it was caught and readjusted, bit of nute burns from that but once you get used to your strain you can tailor the feeding schedule to suit it's needs. I also noticed a calmag deficiency and have upped the calmag i add.

It's basically a fancy swimming pool, you're measuring and adjusting for basically two things with those as well. Ph and ec for growing, or for pools it's ph and chlorination levels.

Damn, I hate to get to the end of a thread just to find out it's 5 years old..

Sativied said:

It should not "should" anything.

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Lol. try again

bernie344 said:

Lol. try again

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Sativied said:

It should not "should" anything. PPM fluctuations are from a difference between water uptake and nutrient uptake amd does not tell you whether the plants need more or less nutrients and means little to nothing by itself. That concept you are familiar with is often referred to as finding the sweetspot, which is essentially just forum nonsense. Instead, run 1.0 EC / 500 ppm and look at the plants (darkness and light tips) and they will let you know if they need more or less. The concentration obviously depends heavily on the amount of water. What matters is the amount of nutrients the plant takes up, the amount in ml you use per week or cycle.

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I have been really struggling with this sativa dominant strain. I am getting what I believe is a burn. I first thought it was a cal-mag deficiency but corrected that. I have tried 1500ppm,1000ppm and now I’m down to 750ppm. I’ll know soon is 750ppm is the spot but all others have shown deficiency problems and burn in this strain. Is the 5.2-5.9ph what you go by? I am having problems figuring out my desired ppm level and I’m getting really frustrated. I now switch do adding full strength micros then topping off with my flower a and B to desired ppm. Anything you might be able to add or correct me on as to why or what I’m doing wrong? Here is a couple pics of what I’m seeing. Thanks for the help!

I should add, everything is great until week 3-4 then the burn/deficiency gets going and fast.

gforce3 said:

I have been really struggling with this sativa dominant strain. I am getting what I believe is a burn. I first thought it was a cal-mag deficiency but corrected that. I have tried 1500ppm,1000ppm and now I’m down to 750ppm. I’ll know soon is 750ppm is the spot but all others have shown deficiency problems and burn in this strain. Is the 5.2-5.9ph what you go by? I am having problems figuring out my desired ppm level and I’m getting really frustrated. I now switch do adding full strength micros then topping off with my flower a and B to desired ppm. Anything you might be able to add or correct me on as to why or what I’m doing wrong? Here is a couple pics of what I’m seeing. Thanks for the help!

I should add, everything is great until week 3-4 then the burn/deficiency gets going and fast.

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I have a way less severe form of what you have in the first pic, burnt tips. I'm in week 6 of flower, and have been mixing about 1250 ppm nute water, only to watch my water drop by half a gallon 24 hrs later and ppm jump to 14-1500. So tonight I decided to do a 24 hr water only flush (hydro guard and cal-mag since using RO water) and going to remix nutes at 900. Just gotta read the plants if she drops in ec then I'm good. But I think you would benefit from a quick 24 hr flush.