Am I taking good care of my goldfish?

Your fish and tank look great! Very nice looking. They won't get much bigger, so even if you keep them in the 20 gal. tank they will do just fine. But if you want to go bigger I am sure they will love it. Looks like you are doing everything great. Goldfish like cooler water, so be sure not to increase the temp., you may want to lower it by a degree or two. As long as they are doing well now I, just keep it up.