Enough with the tank is too small dogmapoo, it's all relative to the present size and growth rate of the individual fish. No two fish ever grow the same. A two inch aro does not need a 250 gallon tank, a 10 gallon will do just fine, so will a 55. Of course there will be some upgrades in the future, worry about it when the time comes. Most fish may take a couple of years to grow up to 12" or bigger. Some say a year but again all relative to the particular fish, how much you feed, has nothing to do with the species. People who overfeed an Oscar will have a bigfoot Oscar in no time. I have an ID that is probably going on a year and he's no bigger than my hand. He can reach up to 4 ft but maybe not for another 5 or 10 years.