Whats a fish that loves to eat fish and more just like a piranha but will still eat flake food (basicly likes fish for treats) that will fit into a 10 gallon?
Dwarf Puffers will attack and kill other fish, but they wont eat the fish, they also dont eat flakes.
If any fish that can eat other fish fits into a ten gallon, the fish it wants to eat will probably be tiny....most freshwater fish will eat fry.
Why are you looking for one?
Red eye tetras can be quite nasty actually, however, not so sure 10 gallons would be big enough for them....
There was a rather nasty incident at work where one of the neons got into the red eye tank, it lasted about 5 seconds, it had been killed before i even managed to get a net.