YES, you can. Did that make you feel better? The Sailfin will probably be easier as they are fairly hardy, I have heard the powder blue are less hardy but I totally understand wanting one, I think they are gorgeous. Now just between you and me, here's my take on the tang thing and the size of the tank, I will keep the fish I want until it becomes too large for my tank and then take it to the lfs and sell it, their is always someone with a larger tank than you who will want it and you can get you another small one to enjoy for two to four years, cheers!