i use a styrofoam one also, dont have any problems with minnows dying off, in fact i bought a dozen pike minnows and 2 dozen crappie minnows and didnt use one of em the whole day, took em home and put em on the bench in the barn, left em there for 3 days and lost 7 crappie minnows and 1 pike minnow, i was suprised how long they lasted, as long as you keep fresh water in the bucket