yep sounds like hydra to me, they come in a variety of colors (mine were light green and very small). simply smooshed them with my hands for those on the glass and put in some ramshorn snails, not sure if it was the snails or the fact that i dont feed this tank much and there is no small food for them to eat, but the population crashed and disappeared in a month or so. i would only worry if you are trying to breed fish or shrimp as the fry are the only thing small enough for them to catch. kinda irritating to look at them swaying in the current on plants though. good luck, and i second mori on the no gouramis, the reccomended 3 spot gets huge and lives forever, i had them in highschool and ended up giving them to a friend with a koi pond.