odd smells in tank

Question
Hi, I have an 80 gallon tank with two gouramis, two catfish, two placasames, one clown knife, two clown loachs, one huge angel fish, and a red tailed shark. the bottom is covered in sand, and I have a 404 fulval, and a 403 fulval filter. I just cleaned the 404, and did a 20 gal change out about a month ago and have been doing about 5 gallons every week since then. the smell is like old seaweed, the fish seem to be healthy and they get along great, should i get rid of the sand and if so how..

thanks
dave

Answer
Dear David,
There may be nothing wrong with your aquarium's smell. As a rule, healthy aquariums should smell like good fresh dirt or an "earthy" smell. This may what your smelling in your aquarium and it may be nothing wrong.
The one thing you must be careful of (I'm sure you are aware of) is to insure your sand bed doesn't become anerobic in spots which are places that become so clogged with debri that oxygen cannot reach there and Anerobic bacteria thrive. These bad bacteria produce harmful gases which can make your fish very sick. Regularly disturbing the sand bed helps keep these problems at bay. You can use the handle of a fish net to stir up places around in the sand bed while doing water changes and siphon the disturbed debri or use the net to skim it all up. Remember that places under stones or driftwood should also be distrubed regularly to keep it oxygenated and clean.

So just remember that an earthy smell is normal and good as it indicates a quite healthy aquarium. Testing your water for any ammonia, nitrites and the nitrate level is always good in any case. But there probably isin't anything wrong at all.

I really hope this helps!
Best wishes and Happy fishkeeping,
Karen~