Biogenic Decalcification

>> Some plants, in the absence of enough free carbon dioxide in the
>> water, are capable of removing dissolved carbonates from the water to
>> provide their carbon needs.  Others can't.  This may also explain your
>> poor plant performance.  This is measurable as a drop in your KH.
>The term used in _The_Optimum_Aquarium_ and a few other resources is 
>"biogenic decalcification" and causes the pH to go UP not down.  

I looked in The Optimum Aquarium yesterday evening to freshen up my knowledge 
after reading this post.  I didn't see anything that said the pH specifically 
goes either way, just that the KH drops to near nothing, making your tank 
susceptible to rapid pH swings.

I can see situations based on this where the pH could either rise or fall, 
depending on other ions in the water.

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc.
(214) 575-3443 (voice)		MSGID:		DAWB
(214) 575-4853 (fax)			Internet:	dwebb at ti_com
(214) 581-2380 (pager)		Text Pager:	pgr at msg_ti.com Subj:PAGE:David