Man these fish really will get aggressive when eating. Just watched it take a krill right out of one of the red head tapajos mouth, and it's only 6 inches. Can't wait for it to get bigger.
I'd say it is unusual indeed for a LSN. They are generally timid fish, even when feeding.
Anyways, your's must be very, very comfortable, relaxed, and bold. You must be doing something very right by it...
Most of these are not happy in an aggressively feeding community, especially if alone. Mine was always thin and miserable, which was before I knew better - these shots are from 2009-2010: