20 Gallon reef

[Diana]

A little overflow area would work, you would be loosing valuable tank space tho.

You could try to rig some sort of surface skimmer attachment onto some HOB filter, such as an aquaclear, and fill it with filter floss and carbon. If you get a big enough one you could even partition it, light it, and have a little fuge in there. I've seen like a tube that comes off the intake at a right angle and then goes directly up to the surface, with a little cage at the top to prevent fish getting in. This pulls water off the surface. But then also have the regular opening at the bottom of the intake as well incase the water level in the tank drops your filter wont run dry.