Just wanted to interject that I've had fish eat young fish - or mortally injure young fish trying to eat them - that were very obviously far too large for them to even consider it.
That includes a minnow that ate regularly, and had not previously attempted to eat an even smaller fish in the same tank.
Thought I'd better mention that, as unpleasant surprises do happen, and sometimes fish disappearances remain unexplained until the perpetrator is caught suspiciously large-bellied AND red-finned...
