Dragon/bar gobies are completely reef safe. Two concerns though. If you have LPS
(or get some later) the goby has a tendancey to drop substrate on the corals irritating the areas between the flesh and sclerites. If the coral is always removing the debris (excess sliming) it will eventually degrade. It can also cause necrosis. The other is if you employ a DSB
of anykind, sand sifting fish/inverts are a big no-no.