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Re: BGA growth in 10 gal tank

Michael Schmidt writes:
> Steve wrote:
> >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.

You have not refuted the assertion that strong light, SOLUBLE NUTRIENTS
and stagnant water encourage BGA algae to grow rapidly! You are just
saying that you have other slightly different conditions where BGA grows
(but perhaps not as rampantly) As I said, there are MANY kinds of
cyanobacteria and some types are able to grow slowly under less than
optimal conditions (for BGA). When you have conditions ideal for
cyanobacteria, you have a very bad mess indeed!!! It can wipe out a tank
in days.

In your situation, it sounds as if your tank is nitrogen limited. It can
still have an abundance of other soluble nutrients including phosphates.
A lack of nitrogen certainly will NOT prevent BGA from growing. In order
to test my assetion I think that if you were to remove your powerhead
and add some manure to your tank (rich in ammonia AND phosphates) that
you could get the walls and everything in your 10 gallon tank coated
with blue-green slime in a few days!!!! I don't suggest you do it mind
you unless you really want to prove a point.

An alternative would be to remove the fish from your 10 gallon tank, add
a little nitrogen or ammonium and perhaps some potassium and continue to
keep the water circulating. As long as no other nutrients like calcium
or magnesium are lacking, the plants should give a little burst of
growth using up the phosphates. I bet you'll see a decline in BGA at
that point. I would also recommend that you manually remove as much of
the slime as possible. It tends to harm plants that it grows on and a
colony of the stuff can persist for a time.

Another way to test my assertion is to set up a 10 gallon with pure
water (distilled preferably) in bright sunlight, no plants, no
substrate, no nutrients. You can set it in bright sunshine with no
circulation of any kind and inject a small big of your BGA into the
tank. It will not flourish. In another container, add some manure,
innoculate and in a couple days, presto! Slime city! [hee hee]

Another more extreme method is to take your same 10 gallon tank with BGA
in it, remove the fish, add snails and turn off the lights for a few
days. The snails should eat the BGA in a couple of days. This isn't an
ideal solution because the snails will also eat some of your plants. If
you don't mind sharing with the snails that's fine. Personally, I like
the Malaysian trumpet snails however they are not the ravenous algae
eaters that the local breed of pond snails are. MTS don't eat the plants
as bad as the pond snails and they reproduce more slowly. I think they
also are more sensitive to calcium shortage in the water.