First Time Saltwater Tank

I've got an Fluval EVO 13.5 G. 12 lbs live rock, live black sand. Ocellaris, yellow clown goby and a Talbots Damsel. clean up crew with a couple of emerald crabs. 1 Ricordia, 1 speckled blue mushroom, 1 other type mushroom, 1 frag of zoa's. I got a couple of pieces of Florida live rock which came with some hitchikers one of which was a thorny oyster. Thought it was a rock to begin with till I saw it move. Hitchikers include, brittle star, a nice patch of feather dusters and some sponges.