Thanks kriswaters, yeah my tank is full of rocks and a yellow tail damsey. I want to put corals and couple more fish in it too. If I put fish in, my yellow damsey will chase all my new fish to the corner and will stress out the new fish (I learned this from other forum, didn't experience it yet). For corals I dont know what to put in yet. I am still searching. Are there anything is easy corals for beginner?