I have a 20 gallon with 1- yellow clown goby, 1-yasha goby and pistol shrimp, 1- purple firefish, 8- barnacle blennies, and yes they do live in a barnacle cluster. All fish have their own hiding holes/territory. I have no aggression issues. The purple firefish cruises the whole tank looking for food. The barnacle blennies are so funny to watch and my favorite at feeding time. I do heavy feeding and heavy water change, 10 gallons every week. Also, all my corals are just softies, zoa's and ricordias, and mushrooms. I do have about 10 rock flower anemones, and they are doing great. But I also stocked all the fish in slowly, which I think helped.