Changing the water regularly and pumping air into it deffinately will help. Keeping the water cold as well as keeping them in plastic or styrofoam containers also helps alot. I trap live bait for personal use and I keep them in an old deep freezer. The trick is to keep the air into them and keeping them as cold as possible. Keeping them cold will minimise how much oxygen they use up. Metal containers that are not insulated will heat the water quicker and does not help you out much at all.