Bugs in my aquarium

Question
I've got these tiny little white free swimming THINGS in my aquarium, they're smaller than pinheads. The seem to stay mostly on the bottom, but I see them swimming from time to time all thru the aquarium. From what I can see, they're round or oval, and apparently swim with some sort of cilia action. They're too small to see clearly tho. They don't SEEM to be bothering the fish, but I'm concerned that they could be a larval form of some parasite. Any ideas on what they are?

Answer
Hi Jennifer;

I don't think they are harmful. Just another "pond critter". I've seen them before too and they just seem to cruise around in the water and crawl, but never on the fish. They probably eat other tiny microrganisms that we can't see.

You might look at these sites to see descriptions and links to various water critters;  

http://www.fishpondinfo.com/micro.htm
http://www.microscopy-uk.org.uk/pond/x_index.html
http://members.aol.com/moresciencestuff/microlife.html
http://www.molecularexpressions.com/moviegallery/pondscum.html

Have fun!

At Your Service;
Chris Robbins