Well, I fixed the flushing noise by drilling the air hole in my Durso one size larger. It seems that I'm running lower flow through it than it was designed for, but that's ok, I wanted a slow flowing sump.
On to more exciting things... I picked up some more rock and finished the aquascaping
And the tank with the canopy in place:
We had the lights on last night so we could enjoy our handiwork, but they'll stay off for the majority of the cycle in an effort to keep the algae down (probably a futile gesture).