Did you say a Mandarin fish? If you did I would defiantly strongly advise you not to get one for a six gallon tank because those fish are very picky feeders. They usually eat only pods and they need a lot of them, I would not recommend it for such a small tank as there isn't going to be enough food for them to eat, so basically they will slowly starve to death. I know you said that you are waiting for pods in your tank to multiply, but sadly there will still not be enough food for a Mandarin, all of the pods would most likely be gone in a couple days. Unless you can manage to target feed them some food, which is almost impossible, but it's still possible. You can still get the fish if you'd like but I just wanted to warn you first.