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Re: Aquatic Plants Digest V3 #300

>I concur with Roger that we can't state in precise terms what stimulates
>BGA growth however the general causes, at least for common types
>indigenous to Vancouver, are well established as an excessive amount of
>soluble nutrients under strong lighting especially where the water is
>stagnant (not moving). This is fairly easy to demonstrate experimentally
>by setting up a bucket of stagnant water with compost or manure in it.

It is also fairly easy to refute by noting that my little 10 gal. tank has
a 78gpm powerhead stirring things up pretty good, and I still get BGA.
What's more, my ammonia is at zero, my nitrite is at zero, and my nitrate
is about 1ppm. So, in some ways, it's about as far (in terms of nitrogen
nutrients and circulation) from a stagnant bucket of manure as you can get.

A check in the archives will show that  other hypotheses advanced for the
stimulation of BGA (low oxygen, high calcium) have counterexamples in the
archives. One exception may be the presence of dissolved organics; because
few people bother to measure these, there aren't any examples of people
saying "I have low dissolved organics and I still get BGA." (The manure
would provide plenty of dissolved organics). In defense of the organics
hypothesis, most of my BGA is growing at the sites of previous other algae
growths, hence at the sites of high availability of organic compounds.

The effectiveness of Mark Storch's hydrogen peroxide treatment may also
argue in favor of this hypothesis, since the H2O2 would tend to oxidize the
organics (to what extent I am not sure). However, it is also well known
that H2O2 is a potent antibacterial, hence its use as an antiseptic.

Michael Schmidt
California State University, San Marcos
San Marcos, CA