PH in my resevoir changes dramatically!!! HELP

Hello All,

I have an interesting problem. I recently (barely) pulled off a harvest after battling a severe outbreak of root rot nearly 3 weeks into flower. After losing 4 of my babies, I quit adding nutrients to my reservoir and only fed my plants water and h2o2 for another 3 weeks. The 35% hydrogen peroxide allowed me to finish my harvest by killing/controlling the remaining pythium(somewhat)... But the weird thing is, after my initial infection of root rot, I have been unable to maintain the p.h. in my reservoir. For example, right before feeding time, I will p.h. my nute batch to 6. Usually, within 2 - 4 hours, the p.h. in my reservoir will have risen to nearly 8! Does anybody have any kind of idea what could be causing this dramatic and rapid change in my p.h. levels? I currently have started 14 new babies, barely 3 weeks old, they seem to be loving the setup thus far, but I still can't maintain the p.h. between 5.5 and 6.5. ANY IDEAS?

I am working with:
three 2' x 4' flood tables covered with black plastic - ebb and flow
all black plumbing
reservoir covered.
room temp maintains about 78 f
reservoir temp maintains about 68 - 72 f
(2) 1000 w metal hallide (1) hps
1 gal smart pots with 4 x 4" rockwoll cubes covered in hydroton pebbles.
all general hydroponics - floragro, vegan compost tea, calmag, superfloralicious,

This is sure is a problem, have you changed your medium, and soaked it in water (ph of 5) for 24 hours, then what nuts are you using, are they stable nuts. Then secondly how often were you cleaning the reservoir.

if ur in a hard water area then the water need time to settle before u know its ph, i have to keep checking mine everyday for the first 3 or 4 days after which it is more stable. some people on here let there tap water sit for a couple of days before using it.. hope this helps a little!

Are you using GH organic cal-mag ?

If so, thats the prob. You should go with Gh 3 part and say good bye to ph issues.

Well, i didn't soak my medium (rockwoll cubes in 1 gal smart pots filled with hydroton pebbles. I change my reservoir every 4 days and clean with h202 to sterilze.

I am actually using GH cal mag. I will switch and see how that works. Thanks!

Thanks for the tip. I usually let my tap water sit out for at least 24 hours before using it. But also, the reservoir i use to let my tap water sit out is only 3/4 the size of the reservoir for my flood tables. So i have to fill the other 1/4 of my flood table reservoir with water straight from the tap. This could be giving me issues as well. But after 2 days in my reservoir shouldn't my ph balance???

I use GH Flora Series nutes. I also used distilled water. On Monday, I got some calmag, since I read on multiple posts that if you use RO or distilled water you need a calmag supplement. Today, I noticed the same problem! I always ph balance the water to 6.0, before I do anything else. Today, I checked the ph in res and it had shot up to 8! So, this is from the calmag?

"since O read on multiple posts that if you use RO" What is O and RO? Sounds like we have a calmag problem to me tho....

coz said:

"since O read on multiple posts that if you use RO" What is O and RO? Sounds like we have a calmag problem to me tho....

Click to expand...

Well, the "O" was a typo, it's right next to "I". RO is just an abbreviation for "Reverse Osmosis". In General Marijuana Growing there is a sticky, titled "Water: The essential compound" posted by Doc111. That was one of the posts I found my info from. Sorry about the typo before, I am horrible at typing on my I-Phone! Anyway, the calmag does seem to be the problem!

Botanicare calmag works better.