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 Post subject: ph question
PostPosted: Feb 17th, '19, 22:59 
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all that i have read says that ph should go down in an aquaponics system. Mine goes up. Did I read the manual incorrectly?

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 Post subject: Re: ph question
PostPosted: Feb 18th, '19, 03:21 
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What media you using?

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 Post subject: Re: ph question
PostPosted: Feb 18th, '19, 04:16 
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You read it correctly. The media may have something to do with what's going on, this could be an algae problem or you could have anaerobic spots in the grow beds.


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 Post subject: Re: ph question
PostPosted: Feb 18th, '19, 05:11 
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in 2 separate systems?
The water from the council supply is ph 8+. i bring it down with phosphoric aicid
as a gwneral rule;
should an aquaponic system of 1700l fish tank, 1000l sump, 600l simple drain,(no bell syphon), 4 dwb of 350 l, qhich direction
should one expect the ph to travel?



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 Post subject: Re: ph question
PostPosted: Feb 18th, '19, 05:25 
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Try adjusting the pH of a known volume of water (maybe in a bucket) and just letting it sit for a day to see if the pH drifts back up. If it does, adjust it again and let it sit. Keep track of the initial volume of water and how much acid it finally took before the pH stopped going up.

Regardless as the fish eat more your pH should start to come down unless you have lots of calcium carbonate (like limestone for example) in your system. If you have coral, shells, limestone or any other form of calcium carbonate in your system the pH will go up and it will be tough for your plants to get the iron they need because of the pH locking out certain forms of iron.


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 Post subject: Re: ph question
PostPosted: Feb 19th, '19, 21:53 
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ty scotty. I have seasheels in my system. I read that they act as a buffer.
I have also added kHCO3.

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 Post subject: Re: ph question
PostPosted: Feb 20th, '19, 05:46 
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Seashells will buffer the water against a dropping pH, but you have the opposite problem.

The potassium bicarbonate you have added will be the cause or at least a contributing factor to your high pH.

You have tried to lower the pH by adding phosphoric acid, but the water is heavily buffered by the potassium carbonate you added, which is why the pH has climbed back up.

If you do as Scotty says, with more acid you will eventually "consume" all the potassium carbonate, which in reality means displacing the carbonate from the hydrogen ions, and the pH will stabilize at a lower figure.

I'd take the shells out for the moment, save them for when your pH begins to drop in the future, but with your top up water at 8+ there might be no point. When your pH does stabilize you will have added potassium and phosphorous to the AP water. As long as the levels aren't harmful to the fish, your water should be in a good place as both are of course key nutrients for flowering and fruiting plants.


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 Post subject: Re: ph question
PostPosted: Feb 20th, '19, 06:26 
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ty. will take out the seashells tomorrow

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 Post subject: Re: ph question
PostPosted: Feb 20th, '19, 06:38 
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Both the shells and the Potassium carbonate effect the carbonate buffer system and depending on where your pH is will cause it to rise. Shells aren't as bad this way but I use them in my system by putting them in a mesh bag that I can remove if the pH starts to drift too high. Hopefully your's aren't mixed in with the media in the grow beds and you can remove them when needed. Shells usually help keep the pH from going down as fast when the nitrification process is going well (fish are eating a lot and water is warm) but every system is a bit different. I still occasionally adjust with potassium carbonate or potassium bicarbonate to raise the pH in my system.

Basically what Danny is suggesting could work depending on your setup. I would remove some of the water and adjust it to a pH of 6.5 to 6.8 using hydrochloric acid. Let the water sit and if the pH changes adjust it back into this range. Once the pH stabilizes add it very slowly, a bit at a time, back into the system. Your goal here is to give the fish time to adjust to the new pH (0.4 pH units per day is probably about as much change as you want). You could keep doing this and eventually (at least we hope) you'll end up with the system water pH where you want.

Just adding acid directly to the system water runs the risk of shocking the fish by lowering the pH too fast.


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 Post subject: Re: ph question
PostPosted: Feb 20th, '19, 07:07 
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the shells are in a box in the sumpImage

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 Post subject: Re: ph question
PostPosted: Feb 20th, '19, 09:16 
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Should be relatively easy to get the pH adjusted then :thumbright: .


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 Post subject: Re: ph question
PostPosted: Feb 24th, '19, 17:30 
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i.ve just read mr. damage on potassium/ calcium deficiency in plants.
As i understand it, you can have calcium carbonate as seashells and khco3 but it will cause the ph to drift up.
so its the lesser of 2 evils; mineral deficiency in plants if there isnt a khco3/ caco3 balance, or every week you have to add some acid to counter the ph up creep (?).

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 Post subject: Re: ph question
PostPosted: Feb 24th, '19, 20:14 
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The addition of the shells and potassium carbonate/bicarbonate is intended as a buffer.

This is to limit the extent to which pH drops as a result of nitrification which is constantly happening in aquaponics. The use of calcium and potassium in a balanced ratio provides the secondary benefit of contributing key nutrients in appropriate balance to the system water. But the primary reason for buffering the water with such substances is to limit pH drop... These substances should not be added to a system with a high pH.

I don't think many people regularly add both alkaline and acid to their systems.

Acids are really only ever used to bring down the pH of very alkaline top-up water from domestic supply when a system is being set up.

The general consensus is not to treat your aquaponics system as a chemistry experiment, but to let the pH adjust naturally over time, only adding buffers like calcium and potassium carbonates/bicarbonates etc once the long term sustained pH drop that characterizes established systems is observed, in order to keep it within acceptable limits.

Fish are able to acclimatize over the long term to pH values within a fairly wide range, but are much more susceptible to rapid pH changes, even when relatively small, and within tolerable/optimum limits. So patience and precaution is a must!


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 Post subject: Re: ph question
PostPosted: Feb 24th, '19, 21:27 
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ty danny. I will not add anything while the ph stays below 7


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 Post subject: Re: ph question
PostPosted: Feb 25th, '19, 09:02 
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Hmm, I'm not sure that was the correct take away in this case. If the pH gets down to 6 then you probably need to raise the pH. If it's below 7.2 but above 6 then you can leave it alone. Most people here use the API Freshwater Master Test Kit which only reads pH down to 6.0 so the actual pH could be lower than the reading indicates (this is when you adjust it up to the 6.5 to 6.8 range).


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