I'm still in the planing stage of a 40B set up. I will use 1 1/2 pvc
through the back wall with a internal overflow, not sure if it will be herbie or durso. For my return I have a Mag 9.5 pump the outlet is 3/4inch so at least that big maybe 1 inch still undesided if over the top of the tank or through the glass. I'm also looking for sugestions, recomndations,and opinions from everyone.