Constantly battling pH drop

[MrShpongle]

I've got a pretty well-dialed in RDWC system that does everything I want except one thing: maintain pH for more than a New York minute. Here's the details.

12 5-gallon buckets
55 gallon rez hooked up to a chiller set at 66 degrees F
Dyna Gro nutes (Bloom, MagPro & Protekt) at 900 ppm
airstones in each bucket + larger stone in rez

When I change the rez out I balance everything to 5.8, and it will stay there for a few days. Around day 5 it starts to drop massively every single day. It can start at 5.8 when the lights come on and 12 hours later be around 4.2! This happens over and over until I change the rez on day 15, then it starts repeating again around day 5. I've used both AN and GH pH Up drops to balance things out, but nothing sticks.

More info: the ppms are remaining solid in the 850-900 the whole time. I top off the rez w/ 2-3 gallons of pH 7 water (120 ppms) each morning to maintain water levels. There is no visible buildup of anything in the buckets or the rez, and the roots look perfect.

I'd like to think that my nutrient solution should be good for more than 5 days. I've considered the possibility of microbial growth in the system, so I've run H202 through the lines in between rez changes, but that hasn't changed a thing.

I'm at my wits end. This has been going on for 18 months, and it's making life difficult. Vacations are a thing of the past...

P.S. This is only a problem in flower.

 

[FRIENDinDEED]

I've got a pretty well-dialed in RDWC system that does everything I want except one thing: maintain pH for more than a New York minute. Here's the details.

12 5-gallon buckets
55 gallon rez hooked up to a chiller set at 66 degrees F
Dyna Gro nutes (Bloom, MagPro & Protekt) at 900 ppm
airstones in each bucket + larger stone in rez

When I change the rez out I balance everything to 5.8, and it will stay there for a few days. Around day 5 it starts to drop massively every single day. It can start at 5.8 when the lights come on and 12 hours later be around 4.2! This happens over and over until I change the rez on day 15, then it starts repeating again around day 5. I've used both AN and GH pH Up drops to balance things out, but nothing sticks.

More info: the ppms are remaining solid in the 850-900 the whole time. I top off the rez w/ 2-3 gallons of pH 7 water (120 ppms) each morning to maintain water levels. There is no visible buildup of anything in the buckets or the rez, and the roots look perfect.

I'd like to think that my nutrient solution should be good for more than 5 days. I've considered the possibility of microbial growth in the system, so I've run H202 through the lines in between rez changes, but that hasn't changed a thing.

I'm at my wits end. This has been going on for 18 months, and it's making life difficult. Vacations are a thing of the past...

P.S. This is only a problem in flower.

your post is enlightening and scary at the same time, for me anyway.

got 8x5gl DWC's for flower and am using it for veg right now. been battling the pH monster for quite some time now with no tds meter. thing have finally leveled out at around 5.8-6.

im actually going the exact same route you are, eventually running 12x5gl RDWC. now im more anxious than when I started!

how are "pH'ing" your water may I ask? it took me about 2 almost 3wks to finally get those buckets with the plants in them to finally level out adding pH down at different doses once I saw that the ph wasn't dropping as fast from the previous dose

ive got a million and one questions and if I could help by brainstorming I will, since we do have a mutual interest in your dilemma.

 

[oldnslow]

ph dropping

ph dropping

Are you sure the nute temp is staying below 75f AT THE ROOTS?? Stick a thermometer in a the root system of a plant. Possibly the chiller isn't keeping the temp down away from the rez. Your symptoms sound like classic bacteria/pythium infestation.

DWC is hard to keep the temp under 75f at the plants. If your pump is sitting in the nutes while recirculating, its adding heat. If your root temps are below 75f or so, that probly means that something else is happening.

 

[Eighths-n-Aces]

http://forums.gardenweb.com/forums/load/hydro/msg040655426466.html

 

[TheCleanGame]

---snip---

 

[MrShpongle]

Temps in the buckets runs between 68-70. They are flooded for 30 minutes every 4 hours with 66 degree solution, then drained back to the rez. The bucket temps just before they are flooded is 70.

As mentioned above, the roots are look pristine and the plants are healthy. If it's pythium, it's presenting in a manner that's never been seen before.

 

[TheCleanGame]

---snip---

 

[MrShpongle]

What's in the water you're using?
Do you have a city/county or water source report?

No signs of slime when you try to maintain pH with pH up or something? Have you tried a bubbler bucket setup off to the side without a plant... just to see what the water and nutes do?

Keep it Clean!

I use city water that is known for being some of the cleanest in the USA. It is fairly soft (120 ppms) so I've never bothered using RO on it (I don't know of another hydro grower in town who does, either). I run regular bubblebuckets/DWC in my veg room with Botanicare nutes and have zero problems with pH. I only change those nutes every 30 days and the pH is rock solid at 6.0 for the full month.

 

[Skunkpassion]

One of two things I would say...

1. ppm to low
2. Root disease

If your roots are good, I would up my nutes slightly ...

 

[MrShpongle]

One of two things I would say...

1. ppm to low
2. Root disease

If your roots are good, I would up my nutes slightly ...

That's interesting. Normally the higher my ppms, the lower the pH in the solution. Do you think that the higher concentration has a buffering effect?

 

[TheCleanGame]

---snip---

 

[mbkboy]

I've got three ideas for MrShpongle. First I suggest you take a look at BigTokes basic water chemistry on this forum. In there he talks about the 'buffering capacity' of water and its ability to maintain pH. Maybe your water has a low affinity to sustain pH? If you can afford the experiment, buy a bunch of culigan (or whichever is cheapest) water barrels and fill your system with that.

My next idea would be to change when your water pump circulates the water. I run my RUDWC for 1 min every 5 mins to never let the water seperate or become stagnant. Maybe you're water is too stagnant and allowing microorganisms to thrive?

How many watts is your air pump, and how many litres of solution is there? Maybe the environment is too anaerobic and also allowing the wrong microorganisms to survive.

 

[Slip Kid]

I've had similar issues with my ph in the past where my ph would drift a few tenths of a point overnight and steadily waver over the course of a few days, usually down. I hand water in coco and mix my nutes in 5gal barrels, one at a time.
What fixed my problem was adding cal-mag to my RO water storage until the ppms are around 250 then using that water as my base mix. I use the same Dyna grow nutes in veg. If my ph drifts up now I know that the lining of the RO barrel will be slippery meaning some algae has begun to grow. I rarely find that it drifts down anymore.
I'm not a microbiologist by a long stretch but I think if the ph is drifting up it means algae if it goes down it's something else. Since I started stabilizing my RO water with cal-mag I havn't had any problems with drift where before I was having to adjust the ph of pre mixed barrels everyday.Now they can sit for days and move only 1/10 of a point ph wise. Anybody can chime in and let me know if I'm wrong on this one but for me it's been a huge relief as I can set a drip to waste without having to worry about my ph dumping. As I said earlier if my ph goes from 5.8 to 6.3 I know my barrels need cleaning with H2O2

 

[MrShpongle]

What fixed my problem was adding cal-mag to my RO water storage until the ppms are around 250 then using that water as my base mix. I use the same Dyna grow nutes in veg. If my ph drifts up now I know that the lining of the RO barrel will be slippery meaning some algae has begun to grow. I rarely find that it drifts down anymore.

I think you might be on to something. Since my tap water has only 120 ppms, there isn't a ton of calcium or magnesium in there. The MagPro takes care of the latter, but not the former. The Bloom only has 2% calcium nitrate, so it could probably use a little more in the form of calcium carbonate, eh? Or even a little baking soda (sodium bicarbonate) to add some buffer?

 

[Thachrizzy]

Without a doubt you are experiencing a microbial affect. Probably bacterial related. The bacteria will convert the ammonium over to nitrates...this frees up the H cation's. As the concentration of H cations increases it will dramatically drop your pH.

Just use some H2O2, or Pythoff. Pythoff is basically chlorine. This will kill ALL microbes including those that are affecting your pH.

Because you are in hydro, and you are feeding fully available forms of nutrients to your plants, the microbes are not really needed.

You could do a foliar application of Hydroguard (Botanicare) to dramatically increase your plants antibody production. This will dramatically increase the plants ability to fight off pest and disease.

Hopefully this helps.

 

[MrShpongle]

I've tried H202 before with no effect. Maybe I didn't use enough? How much H202 or chlorine would you suggest to kill everything without hurting the plants? Years ago I used a little bleach in my aerocloner to combat some brown slime and it killed everything - including my clones.

I'm still going to try the CalMag route first, as it's unlikely to harm the plants.

 

[Thachrizzy]

Use Pythoff...it works better because it persists in your system much longer. When using H2O2 with air stones it will not persist longer than 24 hours. This is probably the reason it did not work for you in the past. Pythoff is super cheap as well.

 

[Thachrizzy]

Oh yes...adding nutrients also adds food for the bacteria that are causing this issue.

I have 20 years growing experience...heavy in hydro...and I have been formally trained in Horticulture...pretty sure my hunch is correct.

 

[TheCleanGame]

---snip---

 

[MrShpongle]

OK, I'll try Pythoff then and skip the CalMag. My only question is if this is pythium or some other microbial growth in the system, wouldn't I have seen *some* symptoms of it other than the pH drop? My plants are huge and gorgeous, the root system is massive and textbook white, the nutrient lines and rez are clean as a whistle, blah blah. How could it be this bad and have no effect on the plants?