I think the worst nutrient trap I found was a sponge filter that I had forgotten about

. Months ago I had switched out pumps when one was acting up. The one I put in there was a
Sedra ksp7000 it can be run as an external or submerge and the thing is huge for only being 700gph. Anyhow its huge because of a plastic housing that covers the inlet when in submerged mode inside the housing is a fairly dense peice of sponge wrapping the inlet. During my cleaning spree yesterday I replaced my pump with the one I repaired and took this guy out for cleaning...
I started with a 5g bucket of clean tap water and no joke I had the nastiest murky brown sludge filling that bucket in about 30 seconds. That stupid piece of sponge took forever to get clean. And I am positive that I haven't cleaned it since I switched pumps atleast 3 months ago.
I wish I could get rid of every damn sponge or mechanical filtration in there. The sponge that is in my sump between baffles is the same way, but gets cleaned a lot more often.
Im wondering if I slow the flow down enough to the sump that it would settle without having a damn sponge in there. Geoff from RC is a huge supporter of bb tanks and helped me out with a lot of set up crap I did wrong swears by a slomo settling area for a sump. I believe he was even making a huge settling tank out of a conical water tank thing that would settle it then whirlpool clean when draining. Cool as hell.
You run your sump with any sponges? Mine is pretty simple. Input chamber w/ skimmer in that first section then about 15 inches till the next baffle which is a bubble trap and area for my sponge mech filter. Since it was an old wet/dry converted I think it would prolly benefit me to have one more baffle after my skimmer. Help keep the damn water height even in the skimmer spot. Just never got around to doing it.
Btw im off the 21st so will be going this month! Unless the wife vetos

, but I think she might actually go with me. She is getting into the hobby slowly but surly I am sucking her in.