Someone who really understands TDS and pH please help!

[BrokrnEyes]

System: top the DWC
Strain: white widow auto flower provided by sponsor AMS

All right, so here's the issue: last Monday I noticed a exponential increase in nutrient consumption from my plant at a rate of 10—40 T DS of nutrients being taken up into the plant every day up till Friday when it jumped from 150 TDS to 297 TDS with a pH of around 6.3, afterwords consumption crashed down to only 8 TDS be used and the ph increasing to 7. The next day it was 58 TDS consumed and the ph was adjusted down to 6. On Monday it or consumed 15 TD ass and dropped the pH down to 7.75. My partner noticed what we assume was nutrient burn appearing in the leaf edges and seen as we typically change the water out on Mondays anyway we change the water and cut the nutrients in half, giving it:

3 ml Flora nova grow
.60 super thrive plant solution
A quarter teaspoon plant revolution great white

This gave us a reading of A PH of 5.5 and a TDS of 677. Today however, checking the pH and tedious of the nutrients in the water, I got this:

TDS: 272
Ph: 6.65
The plant has consumed 405 TDS of nutrients in the space of 24 hours after the water change in what appears to be the beginning signs of nutrient burn! What is going on? I'm half expecting the plant to crash back down tomorrow after seeing this huge increase in plant nutrients being taken up into the plant. This strange cycle began last Monday and while I have seen massive growth suddenly appear on the plant, the fact that there's nutrient burn and the fact that Amilee after such a huge intake the plant practically shuts down it's Nutri consumption I'm getting very worried. I feed the plants twice a week on Mondays and Thursdays so to avoid nutrient firm but it seems like it's still occurring, what's more with the plant not having a regular pattern on how much nutrients it needs a day-to-day basis, I can't predict how much nutrients it's going to need between feedings.

What's more, the pH is swinging wildly now, I did add pH down to the new batch of nutrients to bring it down to 5.5 after I saw that the nutrients only lowered the pH of the water, which had a basic pH of seven, down only to 6.5. So at the very least I would've expected the pH of the water to have camped out at 6.5 and not going any higher.

Can anyone give me any idea as to why this is occurring? Is it the genetics of the plant that's causing the sudden change in how the plant is taking up nutrients? The plant has less than two weeks before it enters it's bloom phase, due to the fact that is an auto flour, and I'm starting to get nervous that if I don't figure this out before the bloom occurs that I'm going to have a hell of a time keeping things in check without the potency suffering majorly.

 

[Papageno]

I think only feeding it twice a week is your problem. Running it up and down like that shocks the plant in a bad way. I am assuming you are keeping the res topped off but not adding nutes every time.

The right way to manage a DWC is to keep topping off with nute solution that is tuned in with the needs of the system. Every top of has some. The total TDS of the res should not change dramatically often. Once in a while fixing a problem is one thing. But if you are topping off with just pH'd water and diluting down the res that will have bad effects unless that is what you are trying to do to solve an issue.

I run easily over a month without a res change. My friend can go the entire grow without a res change. Maintaining a stable healthy res is the key and not running stuff up and down forcibly. Letting the res ease slowly into position is the key. It is because the roots have a concentration of nutes in them that are basically the same as the res.


See this is the issue....the roots don't decide what to take up. They soak up what they are in and become stable with the TDS they are sitting in. when your top off solution Dilutes the res then the roots must leach back stuff into the res which is real bad for multiple reasons. Then after a few days you run up the concentration and they have to restabilize by sucking in a bunch all of a sudden.



The proper way to run a DWC is to mix up top off solution that is tuned for what is happening. So for example lets say you have a healthy stable res running and the TDS and pH stays constant as the water is dropping. then as you top off you add solution that is the same TDS and pH and let it be happy. If the TDS is dropping faster than the water then you need to up the nutes and since it is about the roots concentration you can do so slowly and they will be happy. if the water is dropping and the nute uptake is not happening so the TDS is going up then yes you can add top off with less nutes to dilute it down.

But you never add top off solution without nutes because you are staggering nutes. That is bound to cause problems. you want to maintain the top of solution inline with the res so things don't ever seem to change to the plant.

And in a healthy system the pH is directly controlled by this. The pH will fluctuate up and down in the good range when all is good based on nute uptake and that is fine. but when the system is stressed and the roots are reverse leaching that can cause the pH to go whack on you fast. Usually down fast not up.

 

[BrokrnEyes]

Right, I have a spare tank that feeds directly into the main reservoir that is gravity fed so that whenever the plant drinks water pass a certain point, Grampa B kicks in and the tank refills the lost water. The water is just plain pH water and from what sounds like what you're saying, it's not a good thing to have that set up, should I consider putting nutrient water in the spare tank? Basically makes up a big batch of the nutrients and split it between the reservoir in the spare?

 

[Papageno]

Well that gets real difficult unless you are running a living res. Nutes siting in the spare can get infected easily especially if there is no air pump in there.

I don't have such a big setup I run around 4 plants at a time so I can handle adding a bucket or 2 every day. But yes for those setups what I have read about them is you mix up the feeder res to match what you need and then it takes care of it.

By the way...going to a living res helps a lot with keeping things stable. When I say I go over a month no res change I mean I go well over 4 weeks not adjusting the res pH. It is stable. I only need to adjust the TDS of the top off to keep things happy and the res is stable and needs no adjustment. This is partly due to having a living res which keeps everything clean and happy. I only dump the res "if" something goes south or if I want to change the profile of the nutes. About a week before I switch the lights I like to change the profile of the solution a bunch and instead of trying to force it by topping off with something way different and being at some messy place in between I dump and make a fresh res of exactly what I want. I have the same issue usually mid bloom but sometimes I just do it gradually because by then it can be taking in 1/4 of the res a day so it is easier to update the solution when it is exchanging that fast.


If you are new to DWC give this journal a read. This is a newb who is following my advice to the letter and proving out all of this and more. he is documenting is res readings and has a lot of followers now. I explain everything you need to do DWC in there at some point.

ClosetCase420's - RDWC - 600W MH/HPS - Wonder Woman - Grow Journal - 2015

 

[BrokrnEyes]

No the funny thing is that I was doing this a long time ago with a bunch of regular herbs never thought twice about it, Low back then I wasn't using a pH meter and didn't have a real concept of ph, TDS and so forth. I'll wrap the reserve in foil to keep any light from hitting the nutrients and wash out the tank between every refill to keep anything from building up like algae, as for bacteria, the plan is consuming enough water that I don't think bacteria would have a chance to really cultivate before I'd have to refill the reserve tank.