i have a dragon goby. they are definately reef safe, mines about 71/2 inches long have had him for 7 months now. he doesnt bother any of my coral or my inverts actually he lets my cleaner shrimp clean him all of the time. they are the best sand sifters . the only draw back to them they have bad eye sight so during feeding he tends to miss the food sometime but loves to eat guppies. it is hard to find alot of info on them. He coexists with 1 coral banded shrimp, cleaner shrimp, 20 blue legged hermits, peppermint shrimp, 7 green chromis, niger trigger, very lg tomato clown, about 150 mushrooms,assorted leathers and colts. so you see there is some major deversifacation going on in there and he has never had any problems. plus my sand never looked better.
hope this helps you