Adding ice: Be sure to add a chlorine blocker if you are adding store bought ice. I always add an ammonia/chlorine blocker you can buy at pet stores anyway. Alternatives are to fill jugs with lake water and freeze them, add sealed jugs or treat water in jugs, then add a shad saver too it. With the last option, you actually treat your water as the ice melts.

Many first place their bait in a container, like a cooler, for a time in intermediately cooler water, then add them to a tank that was pulled from the colder depths of the lake. That water will have a better dissolved oxygen content than just cooling top lake water.