Re: Aquatic Plants Digest V2 #380

>Subject: CO2 and Algae


>     I recently created a sudden reduction in the level of CO2 in
>     my tank from the top end of the range given in the "Optimum Aquarium"
>     table (or maybe a little above) to the bottom end of the range (or
>     maybe a little below). Result - no apparent effects on fish but the
>     water turned crystal clear (I never realised it was so cloudy) and
>     large quantities of filamentous green algae disappeared almost
>     overnight. I'm now trying to control CO2 at the bottom of the range
>     and I've added a pH meter to my Christmas present list!
>     My questions are:
>     1) Is this the obvious thing that everybody would expect to happen or
>     do I have an oddball tank?
>     2) Can I expect that now I've got rid of the relatively benign green
>     thread algae, I can expect an attack from somthing really nasty?

>     Jack Hardie in England (don't ask me about the weather - you don't
>     have time)

I have had a lot of experience with problem algae, and most of the species
are not bothered by low CO2 and high pH.  Green water in good light can get
the pH up to over 9, and most of the tough hair algae seem to be happy
without any CO2 enrichment.  It may be that the particular type of green
thread algae you had was sensitive to higher pH/lower CO2, but there are
many other types of nasties that are not.  Was your green thread algae soft
and easly broken, or was it tough and harsh to the touch?

By the way, how's the weather in England?  Maybe it has a bearing on this
mystery, especially if your tank gets light from a window.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
In pleasant Jackson, Mississippi.