Well...I purchased two new fish yesterday. (addiction is tough...) I've got a pair of Orange Spotted Sleeper Gobies. The two of them share living quarters and seem inseparable, so I'm assuming I have a male/female pair.
You can see in the latest pictures, my sand bed is anything but clean. I've long looked for a fish or two that might do the job of munching up the sand. The cuke's do a pretty good job, but they just don't cover enough area fast enough.
These two have gone about immediately building a burrow. In fact, they've surrounded their new home with a good 3" or 4" pile of substrate. It is very dramatic the change in the tank that they have caused in such a short time.
So far, I can't interest them in any food. I'm sure there is a lot of stuff in the sand bed, but I sure would like to see them eating something that I can see.
When they sand-sift, they tend to just sit on the bottom and sift. They don't rise up in the water as they sift, so the sand is generally staying on the ground and not ending up on top of my coral.

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400 gal reef. Established April, 2007. 3 Sequence Dart, RM12-4 skimmer, 2 x OM4Ways, Yellow Tang, Maroon Clown (pair), Blonde Naso Tang, Vlamingi Tang, Foxface Rabbit, Unicorn Tang, 2 Pakistani Butterflies and a few coral gobies
My Tank:
http://www.canreef.com/vbulletin/showthread.php?t=28436