I have had a yellow sleeper goby for about 2 years and he spends all day sifting the sand. Very interesting to watch him do his work! It does make a mess though, and he puts sand all over everything in the tank (like on my live rock, decorations, etc.) But he does keep the sand nice and clean. He did get a bit bigger than I thought he would- about 6 - 7 inches so far.