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Re: G.B.'s view of KH... :)

> From: George Booth <booth at frii_com>
> Subject: Re: KH and hair algae, valisneria
> This implies that bicarbonates and carbonates are not "used up" by plants
> under normal growth conditions. This also implies that bicarbonates and
> carbonates do not need to be replenished on a regular basis unless
> something else is using them (for example, bicarbonates combine with the
> free H+ ions generated during nitrification). 

	That is, the acid generated uses up the "alkalinity" of the
water.  The CO2 is free to come and go, so there is only a significant
amount of HCO3- in solution if there is more cation (positive) charge
than anion (negative) charge on the other ions present except for H+
and OH-.  I'll stress again that for most of our aquaria, we can
neglect carbonate and hydroxide in solution, most of the alkalinity
is bicarbonate.  It isn't even likely that much of it would be other
weak acid anions in most of our aquaria - if we avoid phosphate,
the molecular weights of the complex organic acids that might be
there are so high that the _molar_ concentrations will be pretty
low, and molar concentrations are what counts.

> To me, bicarbonates and carbonates (I like to call them "KH" just to annoy
> the scientists reading APD :-)

	...froths at mouth and tears (what's left of) hair....

	Actually, I don't mind it too much, as long as people understand
what is going on.

> are useful solely to provide buffering and
> to achieve specific ph/CO2 relationships.

	I'm inclined to agree.  

> Some plant books (Baench Atlases specifically) describe plants as requiring
> certain amounts of KH and don't mention GH. I wonder if this is a mistake
> in translation or an author's misconception or if I'm off the deep end. 

	I've wondered about some of the translations in Baensch, too.

Paul Sears        Ottawa, Canada