Although The Grizz may be able to help you quiet down your Durso, I hate to say I mentioned awhile back in your build that Herbies are notoriously easier to deal with
It wouldn't hurt much right now to try some other plumbing, right ???
Herbies don't require downturned pipes or air inlets. Just a submersed main drain. Once the air is flushed, away they go with their full flow
I installed a gate valve on my main drain ( thought I would need it ) and I keep it wide open , with the pump bypassing in the sump as the pump is more than my overflow can handle ( my situation doesn't count here - my sump is only a few inches below my tank so there's not enough pressure to flush the drain )
I keep my main high enough that the box doesn't drain much when shut down and the emerg is close to over-full with a float valve above that to shut off the pump, just in case
Very simple
I haven't had to adjust it once since I started it last month and it doesn't go up and down more than a 1/4" in the overflow box
I wish I could say the same for the level problems I have with the other pump in my sump with the chaeto tank, uv, chiller, skimmer and reactors
