Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
A gentle ripple at the surface, from any source is about right. Enough gas exchange and water movement throughout the tank, but not too much.
I find sponge filter run by bubblers do not create much water movement deep in the tank, but create a lot of action at the surface. I would rather do the opposite. I mostly run Koralia power heads, fairly low in the tank, but aimed slightly up. This will create more water movement lower in the tank with just the amount of ripple at the surface that keeps the scum broken up.