Just purchase 1. Got a little info fm my LFS. Understand it is photosynthetic, requiring the same lighting as my SPS corals also moderate water flow as this is a filter feeder that won't tolerate algae or.being exposed to air. Can anyone offer conflicting or additional advice. I don't have fish, so it won't b picked on. I do have a couple Emerald Crabs that I will keep a close eye on. This is a 30gal. coral tank with a CUC of mostly snails. I always check with AA which never lets me down when it comes to valuable advice. Thanks