The past 2 weeks ive been loosing fish, first one was my flame tail found it with torn up fins stressed and ended up dead, then my twin spot, was fine went to the back of rock pile then found it in the front breathing hard an hour later and a red dot or piece of something coming out his poop hole, now my new purple fire fish went missing saw him in usual spot then gone. the first time i took apart the tank and didnt see anything. latley ive been seeing alot of large bristle worms about 2-4 inches moving around all day, would these attack fish, the ones that keep dieing are the fish that frequent the back of the tank, my clown fish is healthy but always stays up front. any ideas ???