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Adjust PH in a 300 Gallon System...

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I'm having problems keeping a high enough PH in my approx. 300 gallon IBC. I have been doing partial water changes which seem to work short term but I've had to supplement with a liquid PH upper. I need something a bit stronger in order to maintain a constant PH. Any suggestions?

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Several ways to skin this cat.   Baking soda is just about the easiest to find and use.   Calcium hydroxide  (builders lime, pickling lime)  works as well.   If using the lime, take a 5 gallon bucket of system water and add teaspoon at a time, mix and check ph.  Add slowly to the system after letting it sit long enough to turn clear.   The  fine particles can irritate the fish gills , so its best to let it fully dissolve/ or settle and pour off the top.

 

BTW, what is you're PH?  

 

FYI, As your plants mature you will have less problems with ph dropping. Until then, you will likely need to adjust the ph.

Edited by Ravnis (see edit history)

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After a partial water change I can get the PH up around 7. Then as time goes on the PH falls to around 6. I would like to get up to the 7.5 range.

I feed my 6 BG twice a day with a couple pinches of a crumble fish food. I feed them as much as they can eat for about a minute. I have been sucking un-eaten fish food from the bottom of my tank as a white fuzz was forming on it. I thought this was the source of the problem but it's pretty much been taken care of.

I think decaying Duckweed may be playing a role. My pump is too strong so it sucks the Duckweed in and puts them in the bed. I've cleared out all the Duckweed in the tanks but it's impossible to get it all out of the beds it's been deposited into.

As a side note I would really appreciate an organic solution if possible.

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Plants will counter the ph drop to an extent.  The duckweed removes nitrogen and very slowly releases it if it decomposes, so I doubt that is your problem. The nitrification process , ammonia->nitrite->nitrate, acidifies the water, so some way of buffering is required.  Is the system cycled, meaning no ammonia or nitrite detected, and nitrates detected and possibly rising(depending on plant uptake)? Removing duckweed probably reduced how much nitrogen came out of the system, though can't say for sure as I don't fully know the quantities of duckweed produced in relation to your other plants.

 

Some "organic" ways of buffering ph would be limestone rock(fairly good), crushed oyster shell(kinda works, but don't expect big changes right away). There are others, but don't know about them/remember them at the moment.

 

My opinion on "organic" is it's a marketing scheme for an undereducated population that for some reason weren't taught a chemical from a rock released slowly is the same as a chemical released quickly by powdering and removing unwanted ingredients from the same rock. I feel marketers are seriously taking advantage of peoples lack of specific knowledge.  To each his own though, just don't fall blindly for the hype.

 

Ph of 6.4 to 7.0 is about ideal, is there a reason for wanting it higher? Aquaponics will "work"  with a wider range of ph's and plants have less nutrient deficiencies at lower ph (to an extent).

Edited by Ravnis (see edit history)

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There was never a lot of Duckweed in it to start with. As it turns out the water in the tank I had them in goes up and down too much so most of the Duckweed just ended up on the side of the tank. And yes, the tank has cycled.

I will look into the limestone.

As far as PH goes I was under the impression that 7.5 was desirable for bacteria. If 7 is what I should be shooting for I guess I won't need as much as I assumed.

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Just wanted to confirm what Rav said. Your plants will be much happier with the pH 6.8 to 7 and your fish will be fine with it. Once your plants are happy they grow better and the system gets more stable. 

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When I first went down that road, I bought a bag of crushed limestone and put it in a net bag and put it under the water return to the fish tank.  A bucket with holes drilled would do the same thing.  Limestone can often be found in big box building supplies in the garden center.  Oyster shell grit can be found in farm store in the chicken feed isle.  Sand and gravel places might have crushed limestone. You won't need a whole lot for your size system.  A 5 gallon bucket worth should be plenty.

 

Good luck on your system.

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I like oyster shell , a half barrel or so somewhere in the filter line will keep the ph up, rinse it well first or you'll cloud the water, you can buy it in 50lb bags at most feed stores.

 

Jake

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