My suggestion would be to use a design like this one: http://www.radio-media.com/fish/UserHobogatoOnAS-1.jpg
http://www.radio-media.com/fish/UserHobogatoOnAS-1.jpg
It looks like the individual used the water coming back from the overflow to divert some of the water to the algae scrubber. The idea of having it in your sump is good, where are you thinking of placing the lights or light? I would suggest that you will want some plastic near where the plastic mesh and spraybar meet because when algae starts to grow the water can spray anywhere.
Best of luck, I look forward to seeing the pictures when you are done.