They are also apparently fin nippers, which I found out online AFTER bringing my brand new one home from Petsmart. I mentioned we have an angel when I listed the potential tank-mates and BOTH salespeople said it should be fine.
It's tiny right now, but we'll have to keep an eye on it, possibly set up another tank if there is a problem. This guy seems to get along with everyone...so far...
Also, the little description card at PS said max size 6 inches----yet every online resource says 12".

petsmart