i would agree with kickster that they are all "reef safe", however, if you have the burrowing kind, they will dig in your substrate, and if you have like the 4-wheel drive (twinspot) goby, they will eat the live sand in hope of eating the micro flora/faunae, thats in there. Many of them will take to substitute foods, but as long as your cool with this, then id say go for any of them (however some tend to go carpet surfing a little more than others)
good lcuk
jon