Usually people do one of two thing. Run the refug lights 24 hours or run the Refug light opposite the main tank. So when the main tank lights are on the refug is off and when the Refug is on the main tank is off.
Taat2d,
I have a sump for all my junk. No fuge but I keep chaeto in rear of tank (Poor mans version) - not visible from front - w/i rockwork. This uses existing light from tank, critters hide in it & fish feed around it. You can try this first.