I can only try to describe the critters that have infiltrated my tank.
Once upon a time we had a fry tank that got infested with snails, so instead of flushing the snails (and ending up with teenage mutant ninja snails) we set up a dwarf puffer tank. Now that the fry are grown....the former fry tank became a snail breeding tank. Worked wonderfully - just ask the puffer. The tank sits stagnate and lidded. We don't do anything but throw a little food in there now and then - we have hundreds of snails.
However - two types of unwanted critters decided to make a cameo, and I can't tell what they are.
One of them looks vaguely like baby brine shrimp, but they aren't whitish and they're much smaller (smaller than NEWLY HATCHED bbs). They move in the same jumpy manner, but a bit more sharply than the baby brine.
The other is a skinny white worm. It doesn't swim - it merely SLITHERS across the glass. It's about 1/2" long.
Both are horribly gross and I'm not sure if I should just ditch the whole snail tank and start anew.