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Comment by Jon Parr on August 31, 2012 at 5:16pm

Thanks, Nate. Can you recommend a good read explaining all the nuances of pH control?

Comment by Nate Storey on August 31, 2012 at 10:20am

I should say too- carbonates are unique in that they dissolve into and precipitate out of solution in response to pH, so you can have a buildup of carbonates in your system and not know it.  With hydroxides (KOH, hydrated lime, etc.) you get an immediate response from your system pH- this means that you can control the pH very closely and you don't have any surprises.  You also don't have accumulation because the hydroxide is immediately dissolved and cannot build up in systems that dose only in response to solution acidification.

Comment by Nate Storey on August 31, 2012 at 10:17am

You would not want to use straight wood ash.  Instead you would use the ash to make lye- essentially running water through the ash to make lye.  It's not a complicated process, but I would make a lye bin- there's tons of information on making lye from wood ash out there- my wife uses it for soap and many people have posted information on different types of lye bins and the best way to get concentrated lye from wood ash.

Carbonates are bad for beginning systems because they remove a level of control for beginning systems.  I.e. before your nitrification efficiency is up, your related acidification is really weak and carbonates can overwhelm the process, leading to chronically high pH.  (i.e. 8+) which limits nutrient availability and makes it difficult to run your system where it should be- which is below 7 (for commercial systems).

Comment by Jon Parr on August 31, 2012 at 9:36am

Great info. I've got a couple of questions. If using ash as your KOH source, could one use the ash directly in AP, or must you use water steeped thru ash to produce KOH first? Now I'll have to look thru your vids to see why carbonates are bad. Thanks for your time.

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