Five hours after the discovery of little fins inmy tank, and there are still only five. The little one is swimming in circles still.

I'm going to the petstore today to get stuff for them (food, and a possible grow out tank.)

If I do get a grow out tank, what size should I get? Will they need a light hood, filter, heater, ect? Without a heater, temps range from 67-72. With a heater, it climbs to 82. (This is based on a 10g) I currently have no room for another 10g, so would they be ok in a smaller tank? If so, would they require a filter if I plan on doing frequent water changes? Would they need a heater?