I had some for awhile: the cyclops things, some worm like things and some hydra. They either came aboard some plants from a friend or from the snail water from the fish store. I had a real infestation for awhile, but they went away almost as fast as they appeared, wtih no changes to my routine whatesoever. I have two dwarf puffers and about 8 ghost shrimp at the time. Whether they took care of the problem or not, I'm not sure. But ya, thousands wasn't an exaggeration for my 10gal. Some of the hydra still show up, but those are few.

Nice tank by the way!