I've been using locally caught blackworms for a while now. Put them in a container where they will have a lot of surface area, rinse & dump the old water, straight cold tap water is fine. I use a shoebox size container for 1/2 pound, and dump the old water & rinse daily. Keep them in the fridge, covered with about 1/4" of water. No filtration or aeration is needed, nor is dechlorinator needed in the water.
You do need to rinse them a few times when you first get them, they get really rank smelling.