My livewell has a bilge pump pumping water in from the top but I also connect the hose to a piece of PVC that's capped at one end. I drilled a bunch of tiny holes along the length of the PVC pipe for the water to spray out of. I think it helps a lot with aeraerating the incoming water and cooling it off a bit.
Speaking of cooling the water off, I got a tip on the NCBF forum that putting a frozen bottle of water in your well helps a bunch! For the size wells we use, my guess is it wouldn't have to be bigger than a quart.

tight lines
Chris