The longer the dwell time (the time the water is in the bio-media the better (up to a point of course)), so high turnover rates are not good for them. Reserve high rates for mechanical filtration.
.
Improvements... Make sure the sponge is very course.
Loose the carbon unless you have a special need for it.
You can use scrubbies for the whole thing, no need for
bio-balls.
But most of all, use a power head with an aeration
function.
.
Dr Joe
.