Filter behind a filter?
So I'm planning a major overhaul on my 90 gallon. The plan is to put a curved hamburg matten filter in the left back corner, this will allow me to hide a bunch of equipment back there, and then I plan to cover the whole thing with a DIY fiberglass background. My question is, once that is all installed, would I be able to run another sponge filter in the space behind the hamburg filter? I have read that only the first few cm actually do the bio filtration on the hamburg model, but if there is nitrate in the water column wouldn't a second filter work still? Thanks.