More water is better. It shouldn't be so deep the ADF cannot surface for air easily, since they're notoriously poor swimmers.

I think those Fluval U4 filters aren't bad (I use one with my ACF grow-out tank), though Whispers are cheaper and work fine too.

The only thing really "messy" about ADF is over feeding and leaving excess food in the tank, I would just avoid that since it fouls up the water pretty fast.