Ok, I've got a 404 completely disassembled here, . I need a life, hehehe.
Ok, first, here's a little drawing of how it's laid out. The red is the sponges, little boxes on the right are the media trays. Is a 204 similar?
This is how I think the water normally flows. It splits off at the top, some flows through one sponge, the other goes down and through the bottom of the first sponge, then through a tiny gap at the bottom to the underside of the media trays and up. Also a bit probably goes straight into each of the media trays or straight into the outlet.
And THIS is a way that I'm thinking might improve it a bit.
Basically, eliminate the top hole and drill a bunch of holes in the solid tray between the sponges. Then remove the second sponge which is basically redundant because most of the garbage should be trapped by the first(Or leave it, shouldn't make a huge difference) Then the bottom tray either drill a bunch of holes in the side OR cut the top half off and raise it up somehow so there's more room for water to flow into it. Also put a seal between all the trays so the water can't bypass any of the trays and another seal between the tray lid and the water outlet. That should at least(If the seals don't leak) eliminate any water that isn't going through each media tray. Probably would only be a marginal improvement at best, But...I think too much.