Well I'm baffled at what got to this one, everything checked out and the other fish seem fine and the black ghost knife has even become more active swimming around out in the open. But it happens. It was one of the smaller mollies so could have been a number of things I guess.

And the intake isn't big enough to suck up a fish, just it's side fin was stuck in it and well, all of my fish are still pretty small and could get that fin stuck in it.