[Skunk City]

Biggest thing with keeping baitfish alive, as previously mentioned, is maintaining good water quality and sufficient oxygen. Filter and aerator are a must. Over the first 2-4 weeks of running the filter, good bacteria will build up in the filter pads. That bacteria breaks down the ammonia (toxic) released from the fish, making it less harmful to them. Even if you go through a period with no bait in the tank, leave the filter running to keep this good bacteria alive. When you do get more bait, the ammonia levels will not spike and your bait will stay alive. Also, there should be no need to clean the filter any more than every 3 months or so. When you do clean the filter pads, simply rinse them with water from the tanks, not tap water.
I've kept fish, both tropical and bait, for may years, as well as operate a side business doing aquarium maintenance for business/personal, so if you have any questions or need more tips on doing it right, throw me a private message!