COFF, I appreciate the advice on chlorine but since my house has well water I just aerate for 10min and test the water with one minnow before putting them all back in. Haven't had one die due to low O2 with my new pump, but one did manage to wedge itself under the air hose and die at one point.

I scoop any waste out daily to keep the water clean but plan on changing the water out fully once every week or so. It should be an easy process since there is a drain located in the bottom corner of the cooler. Every time I leave home with minnows I end up bringing even more home so the stock is building up slowly

If you want to keep them for long periods of time you'll need a fish tank filter or one like shad tanks use. The shad tanks simply pump water up through a mesh net full of charcoal or a zeolite charcoal mixture to remove the ammonia. Minnows are not as nasty as shad but if you keep them in a container for days on end they will spoil the water with their waste unless it is removed.

I put several dozen very small fatheads in the pool in the bottom of my sister's hydroponic garden with an air stone and they grew huge and died of old age! Even had some babies at one point, pretty sure if I regulated the light and temp they would reproduce...

I bought 5 pounds of fathead minnows to stock my new pond with and the fish farm said they would reproduce 3-4 times a year.
So I bet you are right.

Try replacing 20% of the water weekly instead of all the water so you don't shock them with major Ph changes.

^^^^^

I'll try removing just a portion but haven't had any issues thus far. I do let them acclimate in a mix of 50% old 50% new for an evening before putting them in though. In my head it was more for water temp than pH but that makes sense. All advice is much appreciated I'm looking to get filter soon to decrease the effort put into keeping it going but I have enjoyed working with it so far.

You on right track..Beware of water temp...sudden changes and major changes are deadly

I have a tank that I keep native minnows in as pets. You can find all kinds of baitfish in creeks, spottail shiners, bluntnose minnows, red shiners, baby bluegill, golden shiners, etc and they all work better than the store bought golden shiners, anything but Shad or ghost minnows are easy to keep alive as long as you can keep your tank water cool in the summer and well aerorated.

I have set up a 100 gallon rubbermaid trough with both bubblers and a recirc pump. The recirc pump is a submersible aquarium/water fountain pump that pumps 2800 LH. I think I could use a smaller recirc pump. I have been feeding them dried brine shrimp. So far it seems to work pretty good, but have not been doing it long. I keep it outside in on my back porch in the shade. The water seems to stay cool enough.

Just TWO DROPS of Hydrogen Peroxide will knock out that chlorine quick.......FACT:

It works but I personally have done it with mixed results. There’s always the risk that you overdo it. It’s best to get a good chlorine treatment, or better yet, just put the water in your tank and let it sit open for a couple of days and it will remove the chlorine