i have a snowflake in my 55g, they wont outrite kill your fish, they would however eat some smaller gobies you have or small slow wrasses, but they have very bad eyesight and must be fed by hand, but they are quite interesting, i have no probs with one in my reef but the most common problem of them in a reef is waste production, they are messy additions. On my tank i just run a ASm g2 skimer for filtration and a refugium, and my trates are 0 with the eel, but he is fairly small.
He is actualy my favorite fish in the tank, they have great personalities and it is always fun to feed them.