Mine were marbled gobies, they get a little bigger, are less active and more predatory, One tried to eat my thumb once. The only one I kept for any length of time got to over 18" and ate 12" bass and channel cats, also cat food. also anything that moved, and the heater, and the filter intake, a couple rocks, well you get the idea. I got it for free after my favorite lfs at the time had sold it and had it returned 3 times. The september photo of the month was a marbled goby.