I keep mine in the garage, which definitely has cool temps. I just use my insulated minnow bucket with an air pump/airstone I bought at the pet store. I change around 75% of the water every two days by dumping it out and adding tap water that's been sitting in the garage to reach the same temp. I use "AmQuel Plus" every time I add new water which removes chlorine and also removes ammonia (builds up from fish waste).
I never feed em: 1)It reduces waste and ammonia. 2)They don't need it because at lower temps, their metabolism is WAY down.
Very few of them die, and I've kept them for several weeks between trips this way.