I understand that the 1-3 inch Black moore & fantail goldfish that you see in shops, really grow up to be like 8 inches! Most people who see these little fish dont realize this, & buy them. I want to buy 4 goldfish that are only 1- 1 1/2 inches and keep them in a 5 gallon "plastic" aquarium. I am going to ask for a tank kit for Christmas. The one that has a 5 gallon plastic tank with a black plastic hood, complete with a light & a filter & everything. I only have the room and the time for this size of tank & this size of fish. BUT, here's my problem, I REALLY, R-E-A-L-L-Y want to get 2 black moore goldfish & two fantails(either calico or orange & white), but I only want 1-2 inch ones. Sooo, you guys tell me what you think of my idea:

I will buy the little "baby" Black moores & Fantails that are only about an inch long each, and then when they get to be around 2 inches in length, then I will either trade them/sell them for the 1 inch ones again. What do you guys think??? B)
(I really DO NOT want common or comet gold fish = ( that's why I got this idea)
ALSO, about how long do Black moores and/or fantails take to reach 2 inches from the time they are 1 inch??? And what special cleaning or care do I need to do in order to mank a tank set up of this size work???
Thanks you guys!!! I just want your opinions to add to my decision.
~Petlover333