Help! Little white round, what look like parasites are growing on the side of my tank. What are they?!?

Question

I have had a 55 gallon fish tank since December 2007. Now all of a sudden about a month and a half ago these little white and clear "parasites" started growing on the side of our tank. The tank is not dirty by means and we change our filters regularly. We only have two fish in there and they both seem to be doing fine. We completely cleaned it out once and we bleached the entire tank and basically everything in it. They were gone for awhile but slowly are coming back.

What are they and how do I get rid of them?!

Answer 1

Maybe there egg.........................

Answer 2

How big are they-size of a pinhead or larger?  

Any live plants in the tank?

Do they swim around or are they "stuck" on the side of the tank?

If they do swim, how do they swim-fast,slow, jump around, stay on the sides?  

Are they under water or above the water line?

EDIT:  Oh.....let me provide some kind of answer so the yahoo police don't "violate me" for asking you questions to try to better an answer for you....It could be anything.  More information is needed.  I doubt it's a parasite in the sense of what you're thinking it is though.  Usually when you see something swimming around the tank like that, they're more then likely "scavengers" and not parasites.

Above the water line.....that rules out the normal answers-daphnia, copepods, hydra.  Plus all those with the exception of the hydra, move around and aren't stationary.  Well, I have no idea what you have there, I would say possibly some kind of insect since it's above the water line.  But, they would still move around, most likely.  Here's a link I have saved, try looking through that, but a lot of those are microscopic:

http://www.microscopy-uk.org.uk/pond/x_i...

Good luck!