Awesome thanks for the info !You want the water level in those overflow boxes 1-2 inches beliw the weirs. Otherwise it will dound like a sloshing waterfall. You can order the pipes from Richard’s site.
Home - Durso Standpipes
Durso Standpipes are used to make your aquarium overflow (weir) nearly silent. We help you make your own or purchase them ready made!www.dursostandpipes.com