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[APD] Re: Aquatic-Plants Digest, Vol 4, Issue 93

Giancarlo wrote

> Ammonia, being consumed by 
> bacteria, plants and algae is really the only nutrient that we do 
> not maintain a measurable level of, therefore probably the only 
> element where being the stronger competitor would give you the advantage.

Sorry I can't add much new or constructive to this conversation.  All I can
really add are my doubts.

I have no doubt that *elevated* ammonia levels can contribute to algae blooms
and maybe to subsequent rapid algae growth.  I'm not sure that the reverse is
true; that competition for low ammonia levels results in the absence of algae.
Were that true then I would expect two observations to be common:

1) A planted aquarium equipped with a relatively high-capacity oxidizing
filter (wet-dry) should have very strictly-controlled ammonia levels and
little algae, while a planted tank with little or no added biological filter
should have less controlled ammonia levels and far more algae problems.  I'm
not sure that pattern occurs (with the possible exception of phytoplankton).

2) A planted tank with a light or absent fauna population -- hence no
significant source of ammonia -- that is fertilized with nitrate should never
have algae problems.  I know that this case is not necessarily true.  Algae
seem to grow very well with nitrate as their only significant nitrogen source.

My experience suggests that a tank with nitrogen supplied largely as nitrate
may support different kinds of algae then a tank that is supplied with both
ammonia and nitrate.  While the algae population may be different (and
"wonderfully" diverse) that doesn't mean that the population is smaller or
less of a nuisance.

Clearly something regulates algae growth in a healthy, well-maintained planted
tank.  Ammonia levels or ammonia/nitrate ratios may be part of the
explanation, but I don't think that they provide a big part of the explanation.

Roger Miller
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