-Sleeper gobies but they are messy sifters
-Twin spot gobies not messy but do not sift large mouthfuls
-Diamond goby which is one of my favorite and in my opinion they are the best sand sifters.
I got a glider goby (Sleeper Blue Dot) and it is great. Sifts large mouthfulls and stays pretty much on the bottom so the sand doesnt go everywhere. My sandbed has never looked better.
if you haven't designed your system with this type of fish in mind, you run the risk of having your rockwork crumble and possible crack the tank - they are deep diggers
I am a big fan of the blue dot sleeper as well - OR - bar gobies in 3's - super personality and gorgeous colors.
My sleeper banded goby sifted the sand for the first few months I had him,but I guess he got tired of that and just stuck to the top waiting for me to throw in the flakes, I guess thats an example of the personality they have,indeed a very interesting fish.