Looks Good,
Have you worked out the amount of water the sump has to hold in a power out?? you look like you are clear. Lots come unstuck when the power goes out and the sump over flows
Do as Mr Squigley said and that kills the noise, easy as.
A good Bio mass is 50% shade cloth, works a treat and is all I use and easy to clean. OH I use a pre filter at first contact in the first chamber, Sheets of toy animal stuffing from Spot light cheep and easy and polishes the water well
There is enough oxygen in the water through the sump action, if you want more a air stone under each chamber works a treat.
Bob