this time of year you can circulate the water with fresh and do ok. in the hotter months additives are about a must since you are trying to keep the shad cool. circulating warm water over them and then dropping them down 30+ feet into the thermocline will shock and kill them.
Having a bait tank that can filter is also a plus. The tanks and additives, etc can get expensive but you get what you pay for.
What those additives are, I don't know. Im sure you can do a google search though.