On a different note: Would it be advisable to place a thin sheet of
plastic down the inside of the filter between the baskets and the
sponges? Actually between the baskets and the inside edge of the
'slot' for the baskets? As I said, it looks to me like the water has
a free flow path down the edge between the sponge and the basket
chamber all the way down from the top to the bottom. I am seeing
plant matter that is fairly large (in compairson) that has somehow
made it past the input filter sponges and the media baskets. This
stuff is making it to all 4 layers of media so there is definately
some sore of water bypass going on.

If you pull (stretch) the 2 sponges closest to the media chambers up
slightly, you will eliminate most of this bypass path when the canister top
is in place.

The prefilter arrangement on the '04 series is pretty bizarre but it seems
to work well on both my units. If you look closely, the foam blocks are
spaced from the plastic which allows for many possible pathways through the
foam down to the bottom of the canister.