I Just noticed that in one corner of my tank there are hundreds of tiny little white bugs. I thought it was just algae but when i looked closer thery were all moving. I hope they are only snails an not some sort of parasite or something. I did find one snail in my tank about a couple of weeks back but it was not moving so I left it in the tank. All of my fish seem healthy an not botherd by them. What should I do about this? Should I be worried?