Gobi gobies won't clean sand, your car or anything else. They will poop on it like everything else and they will eat any food they find. They will suck up sand, chew on it and spit out so any particles will be smaller. But they will still be there, including gobi poop.
If you get a diamond goby, there will be sand all over the tank, including on top of any corals you have. If your sand is fine, the water will not be clear because of the constant stirring up of the sand.
If you get a diamond goby, there will be sand all over the tank, including on top of any corals you have. If your sand is fine, the water will not be clear because of the constant stirring up of the sand.
They sift the sand. My biggest regret was adding a yellow watchman to my 29 gal, him and the pistol shrimp make the water cloudy and move piles of sand everywhere, killing frags along the way. I would stock up on nassarious snails, and a few bristle stars.