gravity flow - will this work

[richard kagen]

I am getting ready to start the 20 gallon refuge, filter set up. The display tank has a skimmer to a wet/dry under in cab. I am looking for a mid-water pick up to grab anything floating around - messy eaters
It will sit 12" higher than the display tank. I intend to use a rio plus 1700 to lift water into a first section with filter pad and some coral chunks then just a big old area for live sand , algae, shrimp and maybe a jawfish.
So the question is will a 1" bulkhead fitting thru the tank wall gravity drain back to the display? do I need 2 holes?

 

[chrisnif]

I've done something similar its an "above tank" fuge and it should work well... I'd say nothing more than 100 or so GPH tho as you dont want to have too much current in the fuge