One time I bought a pound of minnows and put it in that cooler and they kept dying I dont know if it was the dirty water quality from the bait shop i got them from or if I got too many minnows at one time and if that's too many what's y'alls recommendations for how many can fit in that bait cooler without dying and yes the air pump was on the whole time . I plan on going fishing sometime this summer

Key is water temp, when I buy my minnows I bring the bucket into the store,, they fill it with the correct temp water and then I will put one hand full of ice in the bucket and turn areator on. And another hint keep water in the bucket on the way to the store so the hot summertime bucket zaps that temp, pour that water out just before you go inside.

Good tips there David!!

You want to add frozen water bottles to the cooler to keep the temp down if your keeping them in the summer.

One other note, I know a guide who uses a shad tank when he's using minnows and he normally buys 2lbs at a time - again he insists on keeping the water colder with ice. You have to be real carefull and not shock them so don't put a lb of ice in there at once or you will kill them.
I'm thinking a lb of minnow is probably around 8 to 10 dozen medium sized minnows, so I think you are good with a 19qt Engle Cooler as far as size goes.
I normally buy 2 to 3 dozen minnows per person when I go and use a Cool Bubbles Cooler and I've never had a problem unless the water gets hot, but another issue I have had is bubbler. I started using the Power Bubbles 12V air pump, it has two air discharge hoses and is the best I have ever used.

POWER BUBBLES X 10.....the best. Hooked to a trolling motor battery, dont have to worry about DC batteries running low.

I carry 2lbs in the 17qt when I run doubles. I use a ton of ice and keep the water uncomfortably cold. Aerators aren’t really that big of a deal to me. Use the stock Engel that leaks and makes a ton of noise. Or a rusty mini bubbles that uses 2 rechargeable double aa batteries that are equally as rusty.

I'm considering one of those cooler igloos, but use the frabil insulated one like this without any issues.

https://www.amazon.com/Frabill-4825...mp;psc=1&refRID=XEMW2BA8T1369D8729PF

I also hit them with a little of the catch and release by sure-life, and don't bother with ice at all

http://www.sure-life.com/products.html