Hello, I currently have a baby fancy goldfish in my 7-gallon aquarium (I know, not an ideal environment but he was given to me as a "surprise" and this was my only tank). The tank is fully cycled, but I just want to know what my water change schedule would be? This is not a suitable tank for this fish, so I was thinking maybe 50% every week. Also, how long can I keep my goldfish in this tank? I am planning to get a 20 gallon in about 2-3 months.