We have kept alot of minnows like that. We use a smaller cooler or med. size cooler. Fill 3/4 of way with water and put a capful of the liquid they use in aqariums to get colorine out (really cheap) and keep the minnows in that with the air pump on. Works great. I even feed them a little fish food like you use in aquarium (really cheap) and last a long long time. Good luck. We have kept minnows up to 2 or 3 weeks