Hi! I'm new to owning a fish tank and have a question. We started off last week with three fish, a black molly, a yellow molly and a female guppy. They were all getting along great! Today we introduced some new fish, five neon tetras, a clown louch(I think that's the name but not sure, it's a bottom feeder) and a crab. They were fine when we first put them in there but since then the clown louch has attacked two of the tetras and eaten off their fins! The weird thing is these fish came from the same tank at the store. Should I be concerned? The guy who sold us the fish didn't mention anything and he has been a great help so far. Is it just normal? The tetras don't seem to be dead either but they can't really swim either. Should I take them out of the tank? Thanks for the help!