This may sound like somewhat of a surprise, but I have a Decorated Goby in my semi-agressive with a Puffah, Lion, and some other fish, and it holds its own. This Goby is somewhat rare, around here anyway, dont see many people with them. And it is tough bastid lol. My friend also has one. They are rabid suckers, and will willingly and forcefully snatch big pieces krill from my Puffah and the Lion. They are by no means timid, and are definitely carnivores that love meat. Even if they hafta steal it from a fish you'd think would be much "tougher" in the tank.And as you would expect, its a plus cuz he helps keep the sand clean.
BTW, my friend tried to put a Lawnmower Blenny in the tank with the Decorated Goby, and the Blenny last less than a month. The Goby was just too aggressive and the bottom of the tank was already "his" lol.