I have a Rubber stock tank. 100+ gallons. Sitting out side the basement here.
If you do not feel the minnows I do not have to change out the water. And use a pond pump from Wal-mart hooked to a home made spray bar. Bar is 1/2" PVC with slits cut into it with a band saw.
Works great and can keep a few pound in it without any problems. Also replace the drain plug with a valve. Just open it and let the water drain out.
Keep a 55 gallon barrel of water that has been sitting for a day or so to refill it with. The minnows do not like city water.
PEte