I use a 48 qt cooler with a 110 volt aerator that I use at the camp. I put 15 dozen minnows in it and never have any trouble. Sometimes I have 2 or 3 dozen left over after 4 or 5 days. I use tap water with a granular chemical I add to it to take the chlorine out. Got it at BPS. I make up the water in the cooler and pour the minnows I got from the bait shop, water and all, into the cooler. After a couple of days, if the water is getting cloudy, or I can smell ammonia, I change about half the water out.