I have a Clownfish who has been living in my 10 gallon tank with only snails, an urchin, and a pistol shrimp to keep him company. I'm transferring them all to a 15 gallon tank. My concern is that he will be aggressive to any new fish added to his home. Would a damsel be an appropriate friend or should I go the docile route and get a goby? Any thoughts would be appreciated!