I have limited experience, so take this with a grain of salt.

I used an Aquatic Life 115 on my old 20L and I was pretty happy with it. Both of my current tanks are filtered by caulerpa prolifera and I'm really happy with that. The key seems to be light dosing of f/w plant fertilizer, like SeaChem Flourish. Of course, in an AIO, you'd have to be content to let it live in the display. I doubt a ball of cheato would have sufficient mass to do what a good skimmer does.