"StringerBell" wrote in message ...
Do you have the sump/overflow ?
This kind of setup is great for skimming the water surface.

No---I have a basic system: Just a Skimmer and a bunch O`rock. Should I
get a 3rd powerhead to aim up at the surface to break it up?

Overflow is best at collecting surface water.

I was actually pondering adding a 20 gallon refugium for under the cabinet.
I have a basic tank, I would need an overflow box for that, right? How do
you prevent floods, by not filling the refugium to capacity?

Overflow box, well designed overflow box is handling this for you.
You just do not fill the bottom tank to the top, so the water
pumped above the teeth of the overflow box will be contained in
the bottom tank when the pump is off.
Bigger problem with overflows is when the U-tube of the overflow
fills with air bubbles and makes water stop flowing down to the
sump - than the bottom pump will pump all the water from the
bottom tank to the top tank overfilling it most likely if there
is no level switch or something like that.