planaria OR maybe something else?
So I noticed a fairly large WORM in my freshwater tank today. Through some googling I think its planaria which I've read is no reason for concern but my question is how do I know if it's a parasite or not? I mean it looks like a brown flat worm and is about 1/2 inch in length (rather big in my opinion) ... Right now I have no fish and this thing mustve stowed away on plant life now in the tank. Anyway, clearly worms are an unsightly animal to many and I am one that shudders a bit at seeing it. Any links to pictures of DANGEROUS worms that could be in my tank?