I just went to my local store and asked for something to sift the sand. They sold me a yellow head sifter goby. My tank is just under 40 gallons, so I'm concerned that he's a little big. He's made a huge mess of my tank in the first 6 hours he's been in there, but I'm hoping the tank will settle and look even better than it did before he "sifted" the sand. He's fun to watch, and quite beautiful, so I hope he works out. besides, I'd never catch him if I decided that he's too disruptive.