I have 4 clowns in my 140g, and I got them over a year ago. they have barely grown in this time. 3 of them are around 4-5" and one is about 5-6". They are painfully slow growers, so as long as you are prepared to make that commitment and definately buy a tank big enough for them, then it's ok to keep them in a smaller tank for a while. Personally I wouldn't do it that way because you never know what may happen in a year or so, but the possibility is there.