Backyard Aquaponics
A place to discuss aquaponics

I believe most plants like a pH of 6.1-6.5, my local pond shop recommends not adjusting pH and letting it work up to 8.0+ because the fish like alkalinity. Where is the happy medium that WORKS?

Also, I have now read TMI on adjusting pH and am willing to simply copy someone else more experienced, especially if someone has already solved my lavarock problem in less than 2 years.
Been using a LOT of this: [Phosphoric acid, Ammonium
dihydrogenorthophosphate (presumed to be a base buffer) and
Citric acid]
http://generalhydroponics.com/site/inde ... wn_liquid/
but citric acid is bad for microbes according to some sources.
I might try this [HCl buffered with bisulfate] http://m.drsfostersmith.com/product/pro ... oCe-Hw_wcB
but plain Ole murit acid is a lot cheaper, though I'd get it if the bisulfate is going to persistently buffer against my lava rocks natural pH 8.0 tendency
what I'd REALLY like is a nice solid acidic tea bag that I can submerge or not as needed, or a buffer media/additive that will reliably cancel the lavas alkalinity.

Id say no one has jumped to answer this one because pH, acids and buffering has been done to death.

Be careful taking advice from pond or aquarium shops due to they are not raising fish for human consumption nor are they trying to grow veg. It is true fish prefer higher pH ranges, as does the nitrification process but its well documented that most of the fish we are growing can happily live in broader ranges so we tend to adjust pH to more so suit plant growth.

Heres a helpful chart showing nutrient availability at certain pH ranges.



Optimal pH isn't really cut and dry. As mentioned, a higher pH is preferable for bacteria growth so that is helpful when cycling and stabilising the system, most systems seem to start out at higher pH levels anyway so recommendations from us early on is to leave it be and let the system develop and in most cases due to the acidic nature of the nitrification process it comes down in time anyways. Bouncing pH levels will cause more harm than good.

When your focus switches to plants this is usually when you want to control your pH into a range best suited for optimal nutrient uptake. There are a bunch of products you can use to do this. As you said, citric acids are no good due to their antibacterial properties, phosphoric acid will work but there are better options by the use of alternating buffers and treating top up water.

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And then there is the other chart. Showing the TAN (ammonia>nitrate) toxicity Vs pH, and showing how badly the toxicity rises as the pH rises..

As Charlie said... it is possibly the most asked questioned point and the most answered ..

Plus one to Charlie's comment to just start a fishless cycling at higher pH and then. Start to control to decrease the pH so that when fish are added, they are less affected by the nitrites etc..

viewtopic.php?f=47&t=25504

And as far as plants and pH is concerned, this is a tabulation of some published material
Eg.. I am keen to grow blueberries well under AP but I doubt I can get the Ph low enuf without killing everything else, so I try a compromise..
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