Filling Red Sea Reefer Confused

[ShaunPReefer]

Hi, I am filling up my red sea reefer and am very confused. We adjusted the water level to the emergency drain and that aspect is all good. The protein skimmer area is up to the brim and is flowing into the large black filter, but water is not flowing from the black filter pad into the return pump section. How is the return pump returning water and is at a constant height although no water is going in that I can see.

 

[Montiman]

I believe that the sump is functioning properly. If you remove the black filter sponge you should see that the water is flowing down through the sponge and entering the return section from the bottom.