sea horses should be put in a species only tank. they are very slow feeders and most fish will out compete them for food also they are extremely difficult to keep. about the only other fish that can be put in with a seahorse is a pipe fish that is it. also with your trigger and lion they would end up becoming snacks. your damsels will probably become snacks also just give the lion a chance to catch them. it does seem like your at your limits now. you have to consider how big the fish are going to get not how big they are now.