They take abut a year to grow out, with quite a burst towards the end, You could easily keep them in a smaller tank while young.
My breeding colony of 6 live in a tank a bit under 15 gal. It is my most stable tank, and the one I need to fuss over the least... apart from hunting eggs.
Heck, I only put a small filter in last week as I decided to keep a few special fry with the adults, ran for months without as I didn't want to filter out the cyclops etc. I managed to keep alive in the tank. Oh and there are 2 pink danio in there as well, they refused to be caught when I moved the rest of their siblings out as fry. They keep the surface and upper areas clean.
Cape Town, South Africa.
Hi. I'm back.