sweet setup, and a sweeter fish room, house remodeling looks great too!, i have the same skimmer and if you add a 1 1/4" T with a bunch of holes drilled out of the bottom of it and a cap on top it will be pretty much dead silent.
Yes, its the outside diameter, fits perfectly in there.
you can see the drilled holes in the bottom, i also added an extender to bring it to the overflow but you won't need it since it's draining back into the sump.
Looking great. You should have buckled the Geo 612 in just in case.. Did you decide on what you were going to do for lighting?
Awesome build so far! It's cool to see someone from rushville on here...Im here in Carthage.
Usually you would go from the display tank to filter socks to skimmer. The refugium would be fed separately from the display tank with a smaller feed and come in after the skimmer and media reactors straight back to the return pump. That way you feed your refugium from the display tank and feed the bugs directly back to the display.
Dave.M