The Neon Goby I picked up from SA at the frag swap is probably the most interesting critter in my tank. He is always wandering around. And when the firefish turns his back, he jumps over and starts picking at him. At first the firefish will just sit there, but after about 5-15 seconds, he shakes the little guy off and warns him away. I suppose a cleaner fish needs a little bit bigger fish than a firefish if he wants to practice his skilz.