NANFA-- large tank problem

William Allen jr. (
Mon, 19 Jun 2000 17:52:43 -0700

Members - WARNING - this may be a rather long message

I'm going to tell y'all what my problem is, give you my diagnosis, my
possible solutions, and then ask if y'all have any better ideas.

I take care (on a volunteer basis) of a 600 gallon native tank at the
Sci-port discovery center, a childrens science/exhibit center. The tank is
stocked with about a dozen or so bluegills up to about 8", maybe 4 white
perch of the same size, a few shad about the same size, and maybe 6 or so
young channel cats about 6", and some green sailfin mollies. we have a few
live plants - some hydrilla, hornwort, and a lilly. Not having a great deal
of luck with plants, probably not enough light.Filtration consists of an
overflow and a large sump with Bioballs, driven by a (very big) Jacuzzi
pump. Sorry i can't be more specific - a local aquarium service installed
everything and was subsequently fired when Sci-port couldn't convince them
that we wanted native AMERICAN fish, raqther than african cichlids, which is
what the aquarium service puts in EVERY tank that they do.
Evidently filtration is doing its job, there is no detectable ammonia,
nitrite, or nitrate. i do a 20% water change every week. The fish are not
overfed - in fact the o[pposite may be true because the woman in charge is
more into herps and still kinda thinks that fish should be fed every two or
three days like a snake! The fish are fed shrimp pellets, flake food, and
sometimes I catch some Gambusia.
PROBLEM - although the water tests OK, there is a lot of suspended matter in
it and a lot of "crud" on the bottom. It is difficult to do a good "gravel
vacuum" because there are several braces across the tank that make working
in it difficult - plus the fact that it's about 4 feet deep and another 4
feet off of the floor!
ALSO, we're getting sick fish - patches of cottony looking fungus.
I THINK that although the water tests OK, that the accumulated crud on the
bottom is harboring bacteria.
SO- can anyone suggest-----
1) a good thorough way to clean the bottom
2) a filter that we can add for mechanical filtration (remember, there is no
usable "rim" to hang a filter on).
3) any meds that will KO the "Fungus" (yes, i know it's bacteria) without
KOing the bacteria bed?

anxiously awaiting your replies,

Bill Allen

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