Why do goldfish need 10 gallons per fish?

Depending on the kind of goldfish you have it is 20 gallons and up. For every other fish you have in the tank with it, it is another 10 gallons. Because you don't even have a 10 gallon yet the panda's growth will be significantly stunted. I don't think it will live for a long time in a less than 10 gallon tank.