Check out my site to see that I did the saem thing you are wanting to do. It has been great as I basically have two tanks set up to view. One is reef safe and the other is non-reef safe.

I use a Mag 18 to return the water to both tanks through my chiller. Both tanks have overflows in them and return to the sump below.

I also use a Mag 24 to send water to the reservoir.

Just click the link below to see everything.