I used to use wild shiners for bass, and they died easily in my live well during hot days. So I got two five gallon buckets, added ice to the bottom one, slipped the other bucket on top and added lake water. This cooled the water above and the shiners became sleepy. I could grab them easily, and about the time they got put on the hook, they began to thrash about.

It was my experience then that fish didn’t need a bubbler if they were cooled. They would last all day long without any added oxygen. It slowed down their metabolism obviously, and reduced their demands for oxygen. I also felt that it reduced their emissions and secretions which no doubt is playing a huge role in your situation. Pumps also produce heat, and can work to warm lake water. A dirty live well could possibly have nasties that inhibit the gills from up-taking oxygen. There are multiples working against you here, that are not as influential when the water is cool.

Maybe sacrifice some of that storage for all them lures ……. for a larger aquarium.