I keep them for long periods of time right in my living room. LOL (I am sure my wife just loves it)
Ive had trouble in the past so I kinda worked out a method that seems to work for me.
I always have 2 5 gallon buckets... One with the minnows and one with fresh water.
I fill the bucket without minnows with water and add a few drops(per directions on bottle) of water conditioner I buy from Walmart.
I always let the bucket sit overnight in the same area as the minnows so it gets to the same temperature.
I find at first you need to swap the water more often due to the feces(They feed them lol) After a couple changes you can wait longer between as long as you pull any dead ones out as soon as you see them.
I dont feed them at all.. If you feed them you will need to change the water pretty often.
Just my .02 so whatever thats worth with inflation.
I live downtownish. Tap water has never been an issue. Even had a couple gold fish last like 6months before nephew killed them and tap water was used to change water every few days. The fridge helps big time. Warm temp kills those simple bastards quick.
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.