Hi! I currently have a young common goldfish in a 20 gallon tank. It is around 2 inches long at the moment, and has been growing since I got him about two months ago. I know that 100 gallons is the correct tank size for an adult goldfish. My parents really prefer that I upgrade over time, though. Is there any reference for a correlation between a goldfish's length as it ages and the gallons they need? Thank you for your time!