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Re: Biogenic decalcification

>From: Elizabeth Worobel <eworobe at cc_UManitoba.CA>
>
>If your pH rises during the day and falls at night, then the rate of 
>uptake of CO2 into the plant is greater than the influx of CO2 into the 
>tank. This creates a CO2 deficit during the day. Biogenic decalcification 
>will ONLY occur if your plants are able to 'use' bicarbonate. 

According to my experience, there is one other place that we should be
aware of for biogenic decalcification.  Certain algaes (red algaes and spot
algaes among them) are quite capable of obtaining their CO2 from
carbonates.  I've had air lift tubes and plastic plants in former tank
setups completely covered in calcium carbonate due to algae growths.  I've
also had Anubias leaves covered with a crusty algae-carbonate formation on
their leaves (a toothbrush and a little patience will remove these
formations).

This calcification can happen fairly quickly (over a period of months) but
shouldn't cause a water-quality problem if regular water changes are
performed.  Algae-calcification can become particularly noticeable in tanks
with large amounts of evaporation, where top-offs are much more frequent
than water changes.  In my tanks, I had algae-calcification as long as I
used airstones for oxygenation.

You don't have to own a reef to grow calcareous algaes.  :-)

David W. Webb           Enterprise Computing
Texas Instruments Inc.  Dallas, TX USA
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