microorganisms in fish tanks

Graham Shepherd muhero at globalnet.co.uk
Tue Mar 13 05:14:03 EST 2001

<UtchWilly at aol.com> wrote in message news:45.37b8392.27de729e at aol.com...
> I am in a Biology class at Fauquier High School, in Warrenton, VA. I am
currently working on a study of the microorganisms in both fresh and salt
water fish tanks. As of yet, I am unsuccessful in finding anything. Is this
an error on my part, or are there no microorganisms in the fish tanks?
> Dutch W.

If there are fish, plants or invertebrates in the tanks there are definitily
microorganisms too.

First, how are you taking samples? Try water from the tanks and scrapings
from the sides and bottom of the tanks. Centrifuge the water samples before
you try microscopy or culture on the deposit.

Secondly, how are you examining the samples? You should be able to see
something using a wet prep (a drop of the sample on a slide with a cover
slip on top) viewed at x400. If you haven't done much microscopy then you
need a positive control (a slide with a known microbe on it) and you may
need assistance with setting up the microscope.

If you're culturing the samples, there are two things you need to be aware
of - the type of medium you're trying to grow the bugs on and the incubation
conditions - you'll probably need several days incubation and you shouldn't
use too high a temperature - room temperature at most. The medium should be
a fairly simple one - a minimal medium with a carbon and nitrogen source, or
a tryptone soya medium (soyabean-casein digest). For salt water you may need
a high-salt medium to support the growth of the microbes.

Lastly, light. You won't grow anything photosynthetic if you incubate in the


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