I'm gonna move them to a big tub when they get too big!
It's not just the size/space issue. In a small tank the wastes will build up to dangerous levels very fast. Larger tanks mean more water to dilute the waste. You should really move them soon. They will get stunted in the 10 gal. I would move them to the largest plastic tub you can get as soon as possible, and then when you get the money, move them to a 55 gal.