I'd like to ask the question of, "What crap?" Are we talking actual :pooh:, or are we talking about algae, or just some extra pellets/food? As far as tangs go, my yellow tang is my only fish that will actually eat pellets off the sand, the rest wait for the current to pick it back up before they peck at it. But if we're talking about algae or :pooh:, my Fuzzy Hermit keeps my sand SPOTLESS :shock:. In fact when I had my sea hare (who actually died from over eating not starvation) his :pooh: would come out in these large size "turle-pellet" looking things, and I remember the first time I saw it, there was an decent sized little pile :grumble:. I was sitting there thinking to myself, "What the hell am I supposed to do with this stuff, I don't want to have to fish it out of the tank every time this guy poops." And before I could even start to look for my net...here comes my hermit straight for the pile and no more than 5 minutes later...clean sand :shock:.
As for gobies, I have no experience with them as the one thing I know about them...my hermit crab might not be the nicest of companions for them :mrgreen:, so I've avoided them for the most part.
To add to your question, I pose this to the actually experienced people in this thread...What about a sand sifting star? I've heard they can be a pain in the :shock: because when they die they kind of just disintergrate under the sand and spike your ammonia...Is this true? Or would a star not be a bad way to go for jimmy as well?