I use an Automatic Bilge pump to pump fresh water in the tank with the tide change. I use one of the Rule all in one Automatic sensing 500 gal pumps. I attached the pump to a 3/4" garden hose and dangle the pump of the dock. The pump needs to be attached to a 12 volt battery and you need to attach a battery charger to the battery. The wire connections need to be water proofed because they will corode quickly or keep the connecting above the high water mark. When the tide gets to a certain level fresh water is pumped in. I have a drain also at they top of the tank to allow the old water to drain out. This eliminates the build up of toxins and also keep the water cooler in the summer. I also get to use natural Charleston salt water. If low tide is mid day it may get a little warm for a few hours but I rarly loose much bait. I have an air pump that runs all the time. I live on a tidal creek that is completly dry at very low tide. If you put the pump down to low it will run too much and burn up. I usually have to buy a new pump each year if it runs mid tide thur mid tide, but it is only $70. It's worth it to have fresh bait at my convinence. Haddrells doesn't sell live mullet. Mullet will last up to 2 wks if they don't die from a fishing hook.