Sounds awesome. The Comet I've had for nearly a year is only 3-3.5" at this point. He went from a carnival fish (Ugh..) to a 2.5g bowl for two weeks or so with daily fin-level WCs, then to a 20L and now a 29g. A lot of reading you do on goldfish like comets, commons, etc, leads you to believe they grow like an Oscar. I feed mine quality flake-food, pellets and freeze-dried tubifex. My 29g barely shows any nitrates between weekly 50% WCs at this point with the comet and fancy in it. Water temp is basically room temp, which can range from the low 60F range to 80F in the summer. My point is, yours might take quite a while to outgrow your indoor setup!