Looking for above tank refuge advise

[saltwater4life1]

Hello guys,
I have been planning on building an above tank refuge. I have a small container that i plan on putting on top of my book shelf that is next to my tank. I have a small power head that i tested about the same head height and got flow so now i'm wondering how to drill the intake and return. Would one tube being higher or lower then the other make much of a difference? All tubing is 1/2" i'm wondering if i have enough tube left over if i should drill a 3rd hole in case the return one gets clogged for some reason?

Here is a picture, (red lines from tank to refuge.)

http://i82.photobucket.com/albums/j247/xskaternickx/fulltankrefugesetup-1.jpg


Thanks guys,


EDIT: Maybe this should of went in the diy...

[micstarz]

Alrighto! Get a pump and put it in your main tank. (figure out gal per hour rate yourself) and use some flexible tubing to connect the output of the pump to the refugium. In the refugium, drill a hole near the top (2 inches from the very top) and put a pvc pipe that leads back to the main tank.

Sorry my explanation skills are pretty crap.