The reason you want to avoid bio balls or other wet/dry media is that they work too well.
They do such a quick job of converting ammonia to nitrate that things like macroalgae or live rock denizens that would also pick up that ammonia and turn it into bio mass don't get as much of a chance. It is always easier for stuff like this to act on ammonia or nitrite than it is nitrate so we want to encourage that where we can.
Is this what your sump looks like:
http://www.petsolutions.com/storefro...pFilters.html#
If you have live rock in a trickle tray like that it will work the same way as bio balls eventually. I'd remove the tray altogether before i used live rock.
I like filter socks even if they are a pita some times, the other benefit is that they remove bubbles. Most of the socks you see have a plastic collar you could use to secure them, I use an old powerhead hanger and a zip tie.