Rule of thumb, here: if it's a predatory fish, IT"S GOT TEETH.
So it drew blood? COOL! I want one!!! No, wait--what about a piranha? Do you think I could fit one of those in my 50 gallon?
I have a slight preoccupation with monsters, by the way. THe biggest one I can fit in my room right now is my pacman frog, though--it gets the size of a baseball glove and has a nice horny tooth all along its bottom jaw. Now HE can draw blood!!! Still, I'm working on finding a bigger monster... I wonder if my mother would let me put a pike in her fishpond. No, no--a SNAKEHEAD!!! yeah...