Oy! I can tell you right now you are going to get a lot of negative responses to this, sorry to say. Chromis need at least a 30g tank, and there really aren't any fish that you can keep in a 5g. And even with a mature 10g (i.e., running for several months) you really can't have more than 3 small fish. Not sure what you could put for live stock in a 5g other than some soft corals, and *maybe* a very small clown goby, but that's pushing it. Please check out the nano fish section on live aquaria to get some ideas for what types of fish you could add to a 10g minimum, and think about upgrading your dad's tank to a 10g so that he can at least have a fish or two that will do okay in that size tank. You can get a 10g for $13 at Petco, not really a lot of money to spend when your talking about the difference between a fish living a full life or dying because they are stressed from being housed in a tank that is too small for them. And please consider returning the chromis.