PH drops in 10g Res

2nd week in on fresh Hydro clones.

Running Single 5G bucket, Flood and drain. I run the flood pump 15 minutes, every 4 hours. It fills the bucket, and overflows back into the res.

PPM = 600 total including faucet water - GH nutrients (Micro,Grow,bloom)
Res = 10 gallon w/ 10" airstone.
Medium = Rockwool (Sat in room temp PH checked water for 1 day prior to use) and PlantIT Hydroton (rinsed until water was clear)
Res temp = Constant 77 degrees (Res is protected from any light penetration)
Air temp = 72 ish

Plant is doing good, and growth seems normal.

Problem is, PH goes down at least once a day (If that's normal, disregard post )

If not, my reading @ 7:00am is 5.6, and 4:30pm it's around 4. I am using GH liquid tester

I use GH PH up/Down to maintain PH level, then using PH up messes with my PPM levels. I test and maintain PH twice daily, once when i get up for work, and once when i get home. In my mind, the larger the res, the easier to maintain PH. Seems it's not so with this. If i am not adding or subtracting any chemicals, why is my PH dropping like so? I use a syringe to pull water from the res to add to my PH tester tube, so i know my hands aren't contaminating the results. Roots are nice and white. (The couple little roots it does have, remember shes 2 weeks old)

I will add, i just changed the res water/nutes 3 days ago, and this is when it started happening. But i used the same faucet water to fill, and wiped the res down and rinsed with hot ass water before use, wiped dry with quality paper towel. I let the water sit in another 10G tote i purchased for that purpose. It sat covered for 2 days prior to adding to my res. 4 more days and i am changing my res anyways, but i would like to nip this in the bud (Pun intended) before hand. I 've heard it could be my hydroton, others say i didn't soak my rockwool long enough. What do you think?


Since this is my first post, i'd like to say Hi also. I am a medical grower/Patient from Michigan (Burton to be exact).

My first thought would be the start of root rot because constant temps over 74 in the res is almost guaranteed to have issues. You need to at least break that heat cycle once a day, try using frozen water bottles. You could have other issues but drops like that with temps like that say res issues. Also look into bennies like aquashield and pondzyme.

What temp should i shoot for?


Maybe i should be looking into a chiller?

Thanks for the quick response by the way!

Also, there is no strange odor, and the roots are nice and white. But the water temp has always stayed right around that range. So it does sound like a breeding ground for issues.

It could be, and probably is the rock wool. The PH of that stuff sucks in my opinion. It takes a lot of maintenance to keep the PH in line, that's why I use clay any chance I get. But seeing as you are there, just keep adjusting because there is nothing else you can do. Next time use clay.

hit the bitches with bleach. a capful in my 25 gallon rez stops the PH from dropping.
Way cheaper and easier than constant teas or using Great White.
Theres only 2 things that make PH drop.
1. your plants drinking so much the PPMs rise and make the PH go down.
2. Funk

Jimdamick said:

It could be, and probably is the rock wool. The PH of that stuff sucks in my opinion. It takes a lot of maintenance to keep the PH in line, that's why I use clay any chance I get. But seeing as you are there, just keep adjusting because there is nothing else you can do. Next time use clay.

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Got cha, I am using the clay pellets, but i used the rockwool to place the clone into the clay. Pretty much to hold it up, and since my pump only runs every 4 hours, i wanted the rockwool to keep my plant damp between feedings.

ilikecheetoes said:

hit the bitches with bleach. a capful in my 25 gallon rez stops the PH from dropping.
Way cheaper and easier than constant teas or using Great White.
Theres only 2 things that make PH drop.
1. your plants drinking so much the PPMs rise and make the PH go down.
2. Funk

Click to expand...

Good info man, thanks!

I've had similar issues with ph drop right after a rez/nite change. It will stabilize within a day or 2 after adjusting with straight water.
I typically do a change using nute-water solution mixed to about 700 ppms left to cycle with a pump for 48hrs prior to adding to reservior. The next day after a nitr change I add straight water because usually my ph will be on the low side meaning the plants are quickly uptaking nutes. This continues until ph is stable usually within about 48 hrs and usually end up around 500 ppms, it seems to be easier to maintain 6.0 ph with lower ppms.
Don't sweat it though, exposing plants to a range of ph is not always a bad thing, unless you let it go so long or swing so far out there is chance for nutrient lock out. Don't get overly obsessed with checking ph...once a day is plenty. Doesn't mean you don't have another problem like root rot but I doubt its your rockwool.

Your staement makes no sense. you say ur ph will be on the low side because it uptakes a lot of nutes just doesnt work. Nutes added to water will make the ph go lower so when plants uptake nutes the ph will go up.

This happens a lot with GH nutes. I used them for years, had to check ph twice a day. Since I switched to AN ph perfect, my ph has stayed 'ph perfect'. Im not trying to start a war here over best nutes, just stating my results.

This thread is a mess of advice... but your water temp is too high for one, so yes look into a chiller or ice bottles and insulate your res... keep it below 70*

Malevolence said:

This thread is a mess of advice... but your water temp is too high for one, so yes look into a chiller or ice bottles and insulate your res... keep it below 70*

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Yes sir!, the same night i posted i threw 5 20oz 3/4 full water bottles in the fridge. Got my temps down and my PH is now in check. You guys are bad asses!. Thanks for all the advice.

Last time i changed my res water i did it right after a flow cycle, and grabbed the pump from the water and that bad boy was warm as shit. I am guessing that attributes to the heat factor. Again, thanks for the advice dudes!

Doobius1 said:

This happens a lot with GH nutes. I used them for years, had to check ph twice a day. Since I switched to AN ph perfect, my ph has stayed 'ph perfect'. Im not trying to start a war here over best nutes, just stating my results.

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Man, you're the 2nd person I've heard say that, the first being the dude at the local hydro store. What's the price like on the Advance Nutrients?

PH perfect will not hold if you have issues with the res. 72 degrees max is what I recommend to my DWC guys. You say your roots are white and no smell...rot may not be the issue. Sanitize all your equipment and switch up nutrient lines and see if that solves the problem Good Luck

Never mind...I'm an idiot and actually have no business interjecting.... I was baked and bored. You are correct I think because I just found the root slime causing my own ph issues. It was white-yellowish bacteria of some sort all over my air tubes. Please disregard my last post and have a great day.

midnitetoak said:

Never mind...I'm an idiot and actually have no business interjecting.... I was baked and bored. You are correct I think because I just found the root slime causing my own ph issues. It was white-yellowish bacteria of some sort all over my air tubes. Please disregard my last post and have a great day.

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Haha, being baked and bored is a good thing!

Your input is always appreciated

No problem! Thx superstoner for pointing out retarded advice and forcing me to rethink. I'll try to be sure I know what I'm talking about before posting in the future....I have much to learn although I sometimes think I'm some kind of an expert...as if lol