Re: [APD] CO2 and pH control

["Andrew McLeod" <thefish at theabyssalplain_freeserve.co.uk>]

> The other reason I like a pH of 6.5-6.6 is that you can keep the KH lower. I
> have been playing with a higher than usual KH for my tank (8-9) just to see
> how my CO2 injection setup is working. If 30 mg/liter of CO2 is good for our
> tanks, per the Krib Table (KH/pH/dissolved CO2). A lower KH is more
> approximate of soft water plant species normal levels, I believe. A KH of 4
> and a pH of 6.6 gives you 30 mg/liter dissolved CO2. I like the idea of
> pumping more CO2 in to maintain that level vs. maintaining a higher KH and
> putting less CO2 into the system. It just seems that  slightly acidic, lower
> KH water approximates the water the plants and fish I keep come from.

Diana Walstad's book has evidence that all plants prefer harder water (after all it is nutrients). The ones that live in softer water are just the ones that cope best!

Also your way of thinking about CO2, pH and KH seems a little backwards to me. pH is just something easily measured that comes about from a combination of KH and CO2 that is easy to measure - it has no significance in itself, it is purely an indicator. I can understand wanting to keep a low KH from some fish (not plants), but then you just work out the target pH from the amount of CO2 you want and the KH, and set for that. KH (and GH) matters to fish, although usually not a lot, but pH does not.

-- 
Andrew McLeod
thefish at theabyssalplain_freeserve.co.uk

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