Is there anything about small butterfly gobies that would be hard for them that anyone knows of? Like do they do better with more than one? I have had 2 die on me and I can not figure out what is going on with them. I have brackish water tank with an albino moray and a leopard bushfish that have been no problems in this tank but when I have added a butterfly goby each time they died the first time within a week and this time just at 2 weeks. I appreciate any advice. I think butterfly gobies look cool.