Need help with my water feature

Hey all. My build is completely done except for one minor problem with my water feature. I designed it with the idea that it would be fed by one of those standard hang on the back filters, this way it could draw water up from below the false bottom, filter it and return it to the water feature.

The design works insofar as the water 'returning' from the filter to the tank goes exactly where I wanted it to go however the filter I bought doesnt seem to have the strength to suck the water up from the bottom of the cage.

I was planning on just going to the pet store and picking up the next model size up, but before I go buy another wrong one does anyone happen to know what the gallons per hour rating would have to be for it to be able to suck water from the bottom of a 20 high?