unexplained PH dives in DWC

[allouez]

Using GH Flora series. Res temps 62F. Multiple but separate single DWC buckets. Generally PH stays steady - I keep around 5.8 to 6.2.

But occasionally, a bucket will suddenly drop to 4.6 or so. Like it will be fine for two weeks, then one day the PH plummets.

There is no rise in PPM... if anything the ppms always gradually drop slightly. Plants look very happy until the PH acts up.

The roots all look fine. No sign of rot. They're always a light beige color, presumably because of the Flora Micro.

Anyone have any ideas why this is happening? What should I do?

Sometimes I'll add tap water and/or PH up, and also add H2O2 or a small amount (1ml per 5 gallons) of bleach. Or I'll change the res. Often but not always it goes back to normal after this, at least for a few days.

But I'm totally clueless on the cause. It's extremely frustrating and is making me consider switching to something like passive hydro.

EDIT: This almost always seems to happen during flowering. Rarely during vegging.

 

[creep]

Perhaps your plants are using up certain nutrients and minerals more than others...

Are you using any additional nutrients or supplements?

Also, are you monitoring TDS and if so are you noticing any fluctuation?

 

[stoney917]

change ur buckets bro ur gonna have issues down the road if u dont . 5gal buckets get a new batch of nutes wkly in flower every2wks in veg.. and u wont have this prob... theres prob nuthin left in there after 1 week i can imagine 2wks of just adding back so they start dumpin shit in makin ur ph drop. i grow 5gal dwcs and they need daily maitenece untill ya dial it in. then ur good for a few days
62 is kidof cool for res temps to 67-70 is ideal i dont know if that can have sumthin to do with it...

 

[allouez]

Perhaps your plants are using up certain nutrients and minerals more than others...

Are you using any additional nutrients or supplements?

Also, are you monitoring TDS and if so are you noticing any fluctuation?

Just PH up/down and GH Flora Gro/Micro/Bloom. My tap water PH is 7.5-8.0 (and 50-90ppm) so I use a fair amount of PH down before adding the nutrients. PH Up mostly just for situations like this.

The TDS gradually drops normally, and when the PH plummets, the TDS isn't too abnormal -- just a tad lower than the day before, except maybe a tad lower than I'd expect. I usually have it 300-350ppm (I think that is over 0.5 EC with this meter) and the plant tends to gradually drop it to the low 200s over a week or so if I let it. I've had burn whenever I've gone over 400ppm and deficiencies under 200ppm. I mix nutes mostly as directed, except only 1/4 to 1/2 strength of what the instructions suggest.

Thanks for the reply, Mr. Creep. My only wild guesses on the cause have been either what you suggested, or maybe root debris rotting in the solution? (some root debris floats around, broken off the roots by the air bubbles) Maybe I'm being too conservative with nutes and that's causing the problem?

change ur buckets bro ur gonna have issues down the road if u dont . 5gal buckets get a new batch of nutes wkly in flower every2wks in veg.. and u wont have this prob... theres prob nuthin left in there after 1 week i can imagine 2wks of just adding back so they start dumpin shit in makin ur ph drop. i grow 5gal dwcs and they need daily maitenece untill ya dial it in. then ur good for a few days
62 is kidof cool for res temps to 67-70 is ideal i dont know if that can have sumthin to do with it...

Yeah I don't know if it's good or bad that the res is that low in temp. I suppose I should I change the buckets more often. Thanks Stoney.

 

[FreezerBoy]

Just some thoughts...

The smaller the res, the faster the disaster. A 5 gal bucket will be lucky to hold 3 gal of nutes. Small res's require more maintenance.

0.5 EC is pretty weak for a mature plant, esp considering you're using the grow bottle which the plant is better off without. If you've ever heard of the Lucas formula, it's based on the Mel Frank/Ed Rosenthal preferred NPK proportions. These proportions cannot be approximated using the green bottle, using Micro and Bloom alone however, gets you real close. That EC drops as it does suggests underfeeding.

You haven't said how you measure pH. If your device doesn't compensate for temps, this could be throwing off your reading. Speaking of temps, you're awful low. See if you can't get them closer to 68ºF-70ºF.

Nutes are acidic and will lower pH by themselves. Add nutes first and adjust pH after. In the absence of disease or rot, there's no need for H2O2 or bleach. Try doing without.

 

[allouez]

Just some thoughts...

The smaller the res, the faster the disaster. A 5 gal bucket will be lucky to hold 3 gal of nutes. Small res's require more maintenance.

0.5 EC is pretty weak for a mature plant, esp considering you're using the grow bottle which the plant is better off without. If you've ever heard of the Lucas formula, it's based on the Mel Frank/Ed Rosenthal preferred NPK proportions. These proportions cannot be approximated using the green bottle, using Micro and Bloom alone however, gets you real close. That EC drops as it does suggests underfeeding.

You haven't said how you measure pH. If your device doesn't compensate for temps, this could be throwing off your reading. Speaking of temps, you're awful low. See if you can't get them closer to 68ºF-70ºF.

Nutes are acidic and will lower pH by themselves. Add nutes first and adjust pH after. In the absence of disease or rot, there's no need for H2O2 or bleach. Try doing without.

Thanks FreezerBoy. I just started hearing about that Lucas formula. I'll try that now. I'll start adding nutes before adjusting PH now too. In mid winter the res temps were 60F (!) but they should get up to 65F or so as it warms up outside now.

I use a cheap General Tools PH501 meter. It says it adjusts for temps. It does drift a little out of calibration at times but when the PH falls under 5.0 in one bucket, it still reads the other buckets as normal. Guess I'll start changing all the buckets weekly and see how things go.

 

[seeyouaunty]

Thanks FreezerBoy. I just started hearing about that Lucas formula. I'll try that now. I'll start adding nutes before adjusting PH now too. In mid winter the res temps were 60F (!) but they should get up to 65F or so as it warms up outside now.

A submersible thermostatically controlled aquarium heater in the res works wonders during the cold months. It'll keep the temps at whatever you set it to.

 

[Young Pumpkin]

As previously stated, nutes first, then adjust ph.

 

[FreezerBoy]

A submersible thermostatically controlled aquarium heater in the res works wonders during the cold months. It'll keep the temps at whatever you set it to.

Shame on me for not suggesting this as I do it myself. In cases of extreme cold, I also cover one of my two intakes which helps the cab to retain some heat.

 

[PoopyTeaBags]

ph drops is a sign of root rot you have any root rot issues?

 

[Agent-Smith]

What buckets are you using? Are they brand new or were they used for food at one point? I know pickle buckets and lemon buckets have been known to cause phantom pH shift when used

 

[Oggy]

i'm sorry but there is no logic in saying that roots need temps in the 68-70 range... that just simply isnt the case... in nature roots sit underground near 50 degrees the lower you go and plants do just fine... mine are kept at a steady 58-62 and they do GREAT... and that temp also prohibits root rot to the point where it never gets a chance to get a good foothold and ruin everything...

 

[allouez]

What buckets are you using? Are they brand new or were they used for food at one point? I know pickle buckets and lemon buckets have been known to cause phantom pH shift when used

Heh... nah they're new. USPlastics I think was the place. Cheapest price for black 5 gal buckets I could find, and they're pretty sturdy.

ph drops is a sign of root rot you have any root rot issues?

If there is root rot causing it, would it be visible? The roots always look fine to me, but I'm a newbie. Very uniform and healthy looking roots, with a light beige color. I figured the beige is from the Flora Micro (makes the solution tinted) but I don't really know.

 

[jm420]

Do What F/B says learn the Lucas formula. Best off to start with a 0-5-10,IME i've yet to find a strain that can handle the 0-8-16.I dont have an issue with the roots staining from the micro but when root rot sets in you will know.As far as your ph meter get some drops or strips for backup, even the best ph meters have screwed people up

 

[FreezerBoy]

i'm sorry but there is no logic in saying that roots need temps in the 68-70 range...

Real world experience by a huge body of growers says otherwise. Plants don't need 50 wsf. Fans don't need 2X intakes. Cabs don't need scrubbers. However, you'll be better off if you provide these things. I've had res temps hit 50 and below. I've had them hover near 90ºF. They do better around 68ºF. Been there, done that.

 

[Midnight]

You can also use this formula for the GH 3 part. It is called the "useless formula", it works for hydro and soil and if you look near the end it addresses one of the issues for ph swings. Iv'e used this feeding routine and it works great.


OK, I figured I would post this here, since some folks are asking about the GH 3 part.
This is my feed schedule -

Here is the nutrient regimen I use and how I control PH with little or no ph up or down...

So OK - feeding schedule week by week. This is the GH weekly feeding program, slightly tweaked. I will only call out the volume of each part per gallon of water in the following manner: grow, micro, bloom, ppm range. Example - 5-2.5-2.5-400/800 would mean 5 ml grow, 2.5 ml micro, 2.5 ml bloom and a ppm of 400-880. Remember it's per gallon. You Euro's can easily convert to liters. 4 liters is just a little bit over 1 gallon. It should also be noted that I use the hardwater micro due to my tapwater. I suggest using the hardwater micro in place of the regular micro if your tap water is over 200 ppm total or you have over 70 ppm Ca. RO water users should use the regular micro.
Veg -
week 1 5-2.5-2.5-400/600
week 2 10-5-3- 600/800
week 3 12-6-3 800/1000 (continue week 3 formula if additional veg time is required.)

Bloom
week 1 6-6-10- 800/1200
week 2 3-7-12 - 1000/1400
week 3 3-8-14 - 1000/1400
week 4 3-8-16 - 1000/1400
week 5 (discussed in detail below*)
week 6 0-7-20 - 1000/1400
week 7 0-6-20 (see bleow**)
* During week 5 if not using a booster like Superbud, Bushmaster Kabloom etc. run 2.5-7-18. I use MOAB (Mother of All Blooms) or BushMaster at 50% of recommended strength, and use 1.25-3.5-9 for the fert base.
**If running an 8 week strain you should only run the ferts during week 7 for a maximum of 3-4 days. This gives you 10 days for flushing. I should note that if I use ferts for a few days in week 7, I take the lants over the 8 week mark. Personally I flush for a min of 14 days. But 10 is bare minimum imo/ime.

The ppms work out almost exactly. I tend to lean toward the lower side of the range, unless I have a really heavy feeder that I know can handle it.

At every ressy change out I add in 5 drops per gallon of 35% food grade H2O2. During flush use ph adjusted water at 5.5-6.0
I will add epsom salt at week 1 of bloom if the plants are heavy feeders AND I see signs of an Mg def. Otherwise I won't use it. The only time I have ever had Mg def is during transition. The GH 3 part is a little low on Mg, but the PBP and Canna nutes are way lower.

Now- how to control your PH...
There are a couple factors that cause your PH to drift. The most common is running the nute solution too strong or too weak. If it's too strong, your PH drops. If it's too weak the PH rises. You have to find the balance point. If you find that theformula above is say, a little strong, and say you have a 20 gallon ressy, mix the nutes for 18 gallons. If it's a little weak, mix it for 22 gallons. You follow?
The other common mistake is mixing your nutrient solution and trying to adjust the PH right away. You have to allow time for the ph buffers in the nutrient solution to do their job. Mix the nutes up, and bubble or circulate for 12 hours before even looking at your PH. You will find the PH to be almost right on target.
I use little or no ph adjusters. (Except during flush). I use tap water, with a starting PPM of 300-400 and a starting PH of 7.4-9.0 (Thats crazy you say! The water is too hard, you will never get stable PH and you will have too much Ca, causing a lockout of Mg!) Bollocks I say.
Every week, on Friday I drain the ressy and fill with plain water. I let that run overnight giving the plants a little flush. This also allows the chlorine and ammonia to evap. On Saturday morning, I mix the nutes into the ressy. I DO NOT adjust ph at this time. Let that run as is overnight. On Sunday morning, I check ph and adjust if needed. Usually don't have to.
Doing things this way has saved me from constant PH drifts, and using about 150 ml of ph down every ressy change, and a little here and there throughout the week to keep it in the desired range. Now, the most I ever have to use is about 30 ml.if any at all. (I have a 35 gallon ressy btw) My Ph stays at a constant 5.5-5.8.

If you are still having PH issues using the above method, an alternative is to PH adjust the plain water to 5.5 BEFORE you add nutes.

 

[PoopyTeaBags]

if the roots are white they ar efine tan isborder line or stained by nutes... youll noticably see shity roots...