Whats in my water??

Question
Hi! I'm wondering... we have an established tank that we took down and set up again with new fish: 2 oscars and a red lobster. (it's a 77 Gallon tank). I'm noticing tiny (a couple of cm's long and as fine as thread) worm-like critters swimming around in the water. Lots of them. My friend (biology student) says something like "nemo...toad..." something or anothers. Is this a problem for my fish? Is this something we can take care of with a water treatment? Is this something my fishes are hosting?

Answer
Hi Liz;

These are a type of "planaria" and are harmless to your fish. They have been feeding on excess waste in the gravel and filter. The only way to get rid of them is by vacuuming the gravel and cutting back on how much food you feed your fish. Without the extra to feed on, the planaria will die out slowly of starvation. Most of us overfeed from time to time and planaria give a kind warning to us. These planaria have served as a warning to me sometimes too. I cut back, do some cleaning and they go away.

Here are some links to learn more;

http://groups.msn.com/FishHealth/planarians.msnw
http://www.aquariumfish.net/information/having_trouble_p2.htm

Followups welcome.

At Your Service;
Chris Robbins