10gal. fuge build

I found a old 10 aquarium I want using and turned it into a refugium. VERY basic as in only 2 baffles- one on the left 2 1/2" from the end-one 4" away from the end. the problem is though I have a small powerhead pumping water into the fuge,the I build an overflow out of pvc to run it back to the sump. I cant get the overflow to work. I think it is because the fuge is in a cabinet about 6" higher then the sump.How sould I plumb this?

 

Well, the fuge should be higher then then sump so the overflow will work; it needs gravity. How do you currently have it plumbed? Can you get a picture of the overflow you made? You need to have water on covering both the inlet and the outlet of the overflow pipe so air can't get back in.