no comment on the sump but i wanted to let you know about my cannister setup that works great....

i took all the stock items out, filled it 80% with live rock rubble, then put the sponge back on top, with a bag of carbon on top of that....

i take the lid off once a month and rinse the sponge in old tank water...

it works great in my FOWLR setup (on top of 2 x powerheads, skimmer) - never had a detectable level of no3...

[it's an eheim 2215 in a 65 gallon tank]