Cleaner shrimp and clownfish, these are the 2 best things I have put in my tank (okay besides my diamond goby who everyone seems to love). Cleaner shrimp are pretty funny to watch, they go crazy during feeding time and will hang out on the rock work, even ride around on a tang (Mine love to pick on the yellow tang). Clowns are generally out, especially the false perculas. I have 2 and they swim all over the place together, again avoiding rockwork. They sleep in the back right corner, same place they picked in the old tank too. They are fun in pairs. My original one was a bit shy until I introduced the 2nd (same with the shrimp), and now they are out and about all the time.