I was looking at my tank and i noticed a few small worm / slug like creatures on the glass...they don't crawl like pods do instead they move more like worms or slugs. they are maybe 2 or 3 times the size of a pod so they are still very small. First i thought i was some brown smuge on the glass and when i used my magfloat to clean it off the thing started to slither through the cleaning bristles on the magfloat and just slither out of it and swam off. Someone at the LFS told me that they might be flat worms. I'm still not sure though i have never seen them before in my tank and they just started showing up. Can anyone tell me what they are and if they are benificial or harmful and maybe how i can get rid of them? THANKS!