I got a medium size insulated cooler and a good 12 volt air pump but every minnow was dead in the morning, How you keepinhg your minnows lively ?
best/joe

Have you tried changing water after about 20 minutes and adding small bottles of frozen water?

What he said.

The water has to be cool. Almost impossible to keep minnows alive overnight in this heat without adding ice. Not too much ice.

Frozen water bottles, change water about every 12 hours or so and BETTER BAIT - Minnow Holding Formula by Sure Life https://fishingproductsandmore.com/products/better-bait-10-oz-bottle-sl102 is what we use when camping in the Magnum Bait Station® 13 https://frabill.com/products/magnum-bait-stationr-13-frbba213?variant=40020463976657 is what we have been using when camping. We lose a few, but works well in this heat

If you don't have well water or water filtration system be very careful about changing water. Chlorine will kill 'em in literally a heartbeat. And don't make the water too cold with ice. That will kill 'em as well.

So, no chlorine I think what I can do is add a frozen unopened bottled water of water, and a cheap thermometer ? what temp range am I lookin for ?
Best/joe

I use the stuff that makes water safe for aquariums if I'm keeping them overnight so I can use tap water and not have to walk down to the pond. Usually one frozen 20 oz bottle every 3-4 hours if you keep them inside. Outside I swap the ice bottles out more often.

Aside from that keep the aerator going strong and don't overpopulate what your size bucket is made for.

Good Luck!

When you buy the minnows, check the water temp. Stay close to that range. 72 works well.

I use regular tap water with a chlorine remover I get from Walmart. I have a aerator and I add a frozen water bottle every 3 hours and keep my minnows live and frisky. Once on the lake I use lake water and frozen water bottles to keep them live. I

One thing here, if that cooler your using seals really good, trouble I had with any aeration was the air got locked at whatever pressure, and it was dead head at the pump. Hard for my blockhead to explain very well. But the aeration pumps would work for a little, the whole time getting slower as time went by, eventually just built up enough pressure inside it matched what the pump could do. The pumps keep running and basically sound ok but no air getting into the water. Make sense?

I have even had the water splashing inside them help seal off the lid to vapor lock the bait tank. I have made me two large bait tanks for here at the house. I had the darm moisture on the backside of the lid roll down and eventually seal that freaking lid on my 50 gallon bait tank and was killing all my bait before I figured out what was going on.

Ultimately the more water, the longer our heat takes to affect it, and the guys are right about the frozen drink bottles to help that. The other if your using any city water, your going to have to treat it, and best give it a few minutes to neutralize all that stuff in it.

I have drilled a few small 1/4" holes in the lids of my big bait tanks which has fixed my issues, with the vapor lock. I am very lucky on the water, I have my own well. The other thing would be lake water, but as already mentioned above the difference in water Temps from what you get your bait to what you put them in your bait tank. Minnows, I have noticed they are much more affected by to much temperature differential.

Bait wells in really nice boats can load up on the best and most frisky bait and when they are idling out through no wake zone or away from the dock and/or ramp heading out to fish they can be circulating water from the lake that like here local is about 88 degrees the last time was there, but that baitwell if full of 75 degree water is circulating with almost 90 degree lake water till they take off as soon as everyone is loaded can shock your live bait till it becomes wormed on bait at best.

Use g juice you can get it online or academy sells it

how's your air stone..I upgraded mine to one that aquariums use (amazon)..siliconed it to the bottom of my Engel Live bait cooler (19 qt)

like others have said, just a few cubes of ice..no need to dump a bunch in..I've never changed the water because I want that water that the bait shop has

This video is pretty good but it might not be practical for what you are doing. Good luck, and please add more info here if you ever get it figured out.