seazo
Newly Registered
Posts: 2
Joined: Wed Nov 25, 2015 6:21 am

Need some chemistry clarifications from the pros here

Hi!

I have this setup home: Image


FACTS:

The water starts in a 40l reservoir, and drips through expanded clay pellets medium, before running back to the reservoir. the driprate is pretty low, and the pump turns on for 30min, and off for an hour - 24/7. The lights are on 18/6.
An airstone in the reservoir is on 24/7 for removing CO2 and adding DO.

I use tapwater, which is basically rainwater here in Oslo. It has very little chemicals, and are pretty soft. (PH 7, KH 2)

The batch I have now, has 50ml per 10l of nutrients.
I've also added some aquarium KH+ to try to achieve a more stable PH. (My PH was decreasing all the time before)


PROBLEM:

The PH is raising high every day. It goes up to as high as 9+. I use phosphoric acid to lower it back to 6,5.
24h after, it's raised back up again.

QUESTIONS:
1. I've read that when plants thrive, they eat more nutrients than water, which causes the EC to go down, and the PH to rise. But will this phenomenon make the water even more alkaline than it was when I tapped it?

2. I don't have an EC meter. Could a Nitrate test for aquariums be a better solution to measure nutrients?

3. I've read that algae can rise PH, and that this can be treated with H2O2. Will H2O2 also affect the bacterias that turns ammonia into Nitrite and Nitrate? This concerns me as I'm eager to move over to aquaponics when I feel I got more control.

4. KH works as a buffer for PH. Does this mean that when I add KH, and then adjust the PH with phosphoric acid or potassium hydroxide - my PH will be more stable, or am I "using up" the KH by lowering the PH?

5. Can my airstone remove enough CO2 that my PH increases significantly? And how long time will it take before an reservoir @ 40l is in DO equilibrium with a single airstone? Are we talking hours, days?

6. When I use phosphoric acid to lowering the PH - will this remove some of the nitrates? If so, which of them, and would it be significant?

7. I've read that you can build a buffer using either a strong acid
and weak base, or a weak acid and a strong base. Is this a way to "lock" the PH? and would it be harmful to the plants if I use too much of these chemicals?

8. Could an unbalanced ammonie/nitrite/nitrate cyclus be affecting the PH?



I hope you have some clever answers for me =) Thanks a lot!

seazo
Newly Registered
Posts: 2
Joined: Wed Nov 25, 2015 6:21 am

Bumping this up in case someone have any answers for me =) Don't need answer on all of them if you have some good info on any of them =)

jhinkle
Newly Registered
Posts: 6
Joined: Sun Feb 21, 2016 11:02 pm
Location: Key West, Florida

Just joined -- may be able to share.

I'm in Key West and am growing hydroponic tomatoes outside (first time).

I experienced an issue similar to what your describe ... get the PH within the window and 24 hours later the PH is 9+.

My situation is that the Florida Keys tap water is specified to be within the range of 9.0 to 9.5.

The water also has chlorimide so I process it thru a RO system to remove it.

I use nutrients from J.R. Peters - they contain a PH buffer. I initially used their PH Down which is Citric acid.

I found the Citric acid was not strong enough to manage the PH where I wanted it. I was adding 6 oz at at time and the PH would swing back into the 9 range over night.

I'm now going to tell you what I did. It may NOT be for you as I used a potent acid that requires extra safety precautions.

I purchased a 1 gallon jug of Muriatic acid for cleaning pools. It will burn you if you are exposed to it. I suggest you research other PH Down agents -- Howard Resh's books list multiple acids that can be used. I found that lowering the PH with this acid allowed the PH to be maintained within my specified limits without swings.

Hope that helps.

Bmullock
Newly Registered
Posts: 1
Joined: Fri Apr 15, 2016 2:33 am
Location: Bali, indonesia

Is it possible to adjust using acetic acid.... Table vinegar?

ladyhawke6281
Full Member
Posts: 15
Joined: Fri May 13, 2016 9:59 pm
Location: Checotah OK-Zone 7A/7B

Hello,

My husband and I are new to the hydroponics world, but we have done a lot of research in the process. We have an outdoor hydroponic system with 143 tomato plants in a DWC system (Dutch Buckets). Also have about 30 pepper plants or so.

Anyway, what we found is humic acid and seaweed added to the reservoir naturally stabilize pH. Our water runs 7.6 and when we fill our reservoir with our masterblend mix, Epsom salt (magnesium sulfate), blood meal, and calcium. When we test the pH it is between 5.9 and 6.0 and stays there. There is no variation in the pH. We have tomato's that we started one month ago and we already have flowers and tomato's. It's worth a shot.



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