OK.. sorry I took so long.
Here are the pictures of my buffer. I use an aquarium grade sponge.. I highly suggest you use a sponge similar to this.. you want the water to be able to flow through it easily. Make sure you boil the sponge before adding it to your tank just to make sure there are no bacteria etc that could harm your fish.
as you can see there are notches cut so that the sponge hangs straight down. It just barely touches the top of the water.
make sure the rubber bands do not impede the movement of the biowheel.