pH out of control. No idea why its climbing so hi so fast.

[Mike20132]

I fear I may have lost my grow... What at first looked like an iron deficiency has turned into a much larger issue. I am hoping some of the more experienced minds here can help me before the plant starves much more.

The lower leaves and branches are starting to drop and get brown spots (new symptom) on top of the new growth being a pale yellow.

I am growing DWC in a 2 gallon res. Plants are now at least one week into flower.

600 Watt LED
Advanced Nutrients (1.5 mL across the board. was going with 2.0 when the problems started)
Distilled water
Nutrient mix Ph is usually a tad below 6.

Within 12 hours of draining the res and filling with fresh nutrients, the pH has jumped to over 7.5. I cannot seem to bring it down using pH Down (adding 1mL after every reading, and it does not seem to be getting any lower for very long)

This really looks like the nutes are completely locked out, due to the high pH.

What is really confusing me is how it could be rising that fast! Am I looking at a possible infection? (Algae, etc)?

Pretty bummed to watch the girls die after they were going along so well for so long.

Any help would be immeasurably appreciated.

 

[woody]

@Mike20132 are you monitoring ppm/ec at all mate?

 

[Mike20132]

@Mike20132 are you monitoring ppm/ec at all mate?

Yeah. It did get rather high, but that was two weeks ago. I flushed the res out then, and there were a lot of nutes (though darker in color). This was about a week after I started using organic calmag. I have switched to calmagic+ (to increase the iron, which looked like the original problem).

With PPM, I watch for it to change from the original concentration after 12-24 hours to see if its taking up more water or nutes, and try to adjust the mixture to compensate. The nutes are ph buffered, but it looks the alkaline buffer agent is being depleted in short order.

With this most recent flush, I went with 1000ppm (or 25% less nutes), with a starting pH of about 5.6. 12 hours later its up to 7.5. I wouldn't think going much lower than 1.5 mL/L of the nutes would provide enough, but I can certainly try going even lower. And with the elevated pH, it was no surprise that the PPM climbed as well. Though the cause of the elevated pH could be too high PPM. Sort of a chicken and egg problem.

I could be completely wrong about what is going on. This is my first grow, and I am learning from my mistakes. One mistake I won't make again is DWC in such a small res. If I can salvage this grow, that would be wonderful, but I am starting to get the feeling that I've been done in by my choice of res size. Around half of the total volume of the res is roots. thats not much water/nutes left to buffer any sudden changes.

 

[woody]

Your right there- the smaller the res the harder it is to keep it stable.
If the ppm is rising fast i would lower it again to maybe even 800 and see how the plant reacts.
Although if the res is too hot i would expect ph to drop not rise

 

[Mike20132]

Your right there- the smaller the res the harder it is to keep it stable.
If the ppm is rising fast i would lower it again to maybe even 800 and see how the plant reacts.
Although if the res is too hot i would expect ph to drop not rise

I just discovered another problem - and I have my fingers crossed that this is going to help.

The rez has a built in circulation pump, but it has a reputation for getting clogged with roots and is apparently difficult to replace.

So in its place, I have been using a rather large air-stone.

I have a feeling that once the root mass got so large, the stone could no longer circulate the nutrient solution properly. I also noticed a reasonable pH level when the sample was taken near the edge of the tank. Makes sense if circulation is bad. I've turned the pump on. I'll gladly sacrifice the pump to save the grow, since I wont be using this res again in future grows.

I'll post a followup later tonight if I see any improvement in plant health. It's very droopy now, and I expect that should recover somewhat quickly if I can break the nute lock in the core of the roots.

Thoughts?

 

[woody]

So the roots could have been getting less oxygen than they needed- that would cause some problems for sure man. Keep us updated!
Also have you calibrated your ph pen recently? Im sure you have but thought i would mention anyway

 

[Mike20132]

So the roots could have been getting less oxygen than they needed- that would cause some problems for sure man. Keep us updated!
Also have you calibrated your ph pen recently? Im sure you have but thought i would mention anyway

Funny you mention that. Either I have no idea how to use a pH pen properly, or both of the ones I have tried are faulty.

When the pen is dipped into solution, it reaches a point where it continues to drop .01 pH every few seconds, and never seems to actually stop at a reasonable place. For now I am using the ol' test reagent and color chart method. It's good enough to at least tell me when it's in a safe zone, but eventually I would like to have a pen that works. I do keep it calibrated, and it seems to take to that rather well. I've never let it dry out, and I store it in the manufacturers recommended solution.

I was thinking it may be the pH buffering agents that are slowly dragging the reading down in my small sample. No idea though.

Thanks for the help. I'll post an update later.

 

[Waira]

... need pics mate,.... And I'd check the nutes for fouling, in Di water, the AN should be plenty stable,... super weird to be getting such jumps in alkalinity.... meters should be OK if you've maintained them properly,.. calibration solutions OK too? 7.0, and 4.0 are what I use,....

 

[Rev. Green Genes]

Funny you mention that. Either I have no idea how to use a pH pen properly, or both of the ones I have tried are faulty.

When the pen is dipped into solution, it reaches a point where it continues to drop .01 pH every few seconds, and never seems to actually stop at a reasonable place. For now I am using the ol' test reagent and color chart method. It's good enough to at least tell me when it's in a safe zone, but eventually I would like to have a pen that works. I do keep it calibrated, and it seems to take to that rather well. I've never let it dry out, and I store it in the manufacturers recommended solution.

I was thinking it may be the pH buffering agents that are slowly dragging the reading down in my small sample. No idea though.

Thanks for the help. I'll post an update later.

I went through several pens, and had all sorts of trouble with pH for a while there. get a good pen, one with temperature compensation. Don't measure in the bubbles, and take good care of the bulb sensor, rinse after every use.

here's a link to a review I did on mine:
https://www.autoflower.org/threads/ggs-giant-greens.59188/page-7#post-1555352

Sometimes calmag will cause that overnight up spike. It's happened to me several times. Sometimes it takes a while to change, you can add several capfulls of pH down before you know it and swing back the other way and get 4 pH.

I am still confused by this because in theory calmag should lower the pH. But if adding it to a reservoir with nutes at a high PPM, it is having some kind of reaction in there that makes it go up.


perhaps this helps. perhaps it's crazy, and I misinterpreted the problem.

 

[Mike20132]

... need pics mate,.... And I'd check the nutes for fouling, in Di water, the AN should be plenty stable,... super weird to be getting such jumps in alkalinity.... meters should be OK if you've maintained them properly,.. calibration solutions OK too? 7.0, and 4.0 are what I use,....

Sorry it took so long to get these pics up. Just got home.

The pH swings have me perplexed as well, but interestingly enough the exact same thing that green genes reported in the post just below yours happened to me. As soon as I started supplementing with calmag, the pH went absolutely crazy. I added way more than enough pH down to correct the problem, and yet it stayed pretty solidly above 6.5 for the entire evening. The next morning, it was down to at least 4.0 (that is as low as my testing solution can indicate). I immediately emptied the rez and flushed out with distilled water before adding more solution.

At the time I suspected the calmag might be at fault, but assumed that the pH buffering of the nutes would correct it. Even with copious amounts of pH down, there was no change until the dramatic overnight swing down. I suspect this may be due to a depletion of the acid buffering agent (after the calmag probably depleted the alkaline buffering), but that's just a guess.

Turns out the calmag I was using was organic-based. Another mistake I wont make again. So when the initial symptoms started to appear (the yellow new growth), with the help of others on this forum we determined that it was likely an iron deficiency. At the time the lower growth was not impacted as shown in the pics on this post. With the fact that I was using organic calmag combined with an iron deficiency, it seemed appropriate to switch to general hydro calimagic, as it included some additional iron. i do not believe this formulation is organic-based, but I could be wrong. I still seem to have the pH issues, even with the calimagic. At this point, I might just stop using it. Any benefits so far are clearly outweighed by the damage it has done to the plant, if it indeed is the culprit.

I have been flushing out the res frequently while trying to fix the plants, so I don't think nutrient fouling is suspect, though I might be misunderstanding what you mean by that.