There are a few that could work out in there. Hawkfish are an agressive fish that people often over look. They are full of personality and make nice additions to smaller sized tanks. You could also look into dwarf lions. Some may say a 3' tank is a little too small, but with the right tankmates, it should be fine. Some smaller eels (goldentail comes to mind) would also work out. Give us a little more info on your tank as well. Is it already set up? How much liverock, etc. HTH. Bo