Left minnows in my livewell from last Thurs to today. All survived and were frisky. I know the cool weather made it possible. I plan to keep doing it until it does not work. Sure beats releasing left-over minnows into the lake, then buying more for next trip.

Reminds me of a funny story...
I knew some guys that would go trot-line fishing each year to catch enough catfish for a very large fishfry for their company. They would buy hundreds of dollars worth of bait fish (minows and gold fish) and transport them in a large stock tank. Like what you would water cattle out of. One of the guys purchased a large amount of ice to cool the water down while in route to where they fished. Shocked all the bait fish and killed them. I guess the water can get too cold. LOL

Ice has chlorine in it... it will kill fish fast but if you get bags of ice and leave it in the bag you're usually alright if they are mostly sealed. I helped move a carp from Town Lake in Austin to Cabelas Ft Worth in the heat of summer and she made it just fine with bagged ice.

Just freeze 2 liter drink bottles full of water & drop them in to keep the water cool & minnows will survive.

put minnow bucket in the ice box will keep along time