I cup to 30 gallons is a good ratio of mixture. Most bait dealers can order this or will have some form of chlorine killer. The most popular type is from Jungle called Bait Saver. It's cheap, and it kills the chlorine before you put shad m the tank, not after. Water temperature should be kept 65 degrees or less at all times.
Warm water means lower oxygen levels.
Cool your water by adding ice, but do it slowly, rapid temperature change can result in shock or death. 3 degrees per minute is a good guideline. Buy an inexpensive temperature gauge. This can be a valuable tool to have. This mixes the water and adds oxygen- Paddle aerators work well but can beat the scales off the bait.