No bio Balls, need cleaned off to often to be effective at anything. Get several replacement filter pads to swap out and clean weekly. You can also use LR not just rubble, my trickle chamber has 1cu ft of LR in it. I also use chemical media - Chem-pure elite for Nitrate, Po4, and Silicates. I have a trickle tower but the rest of the sump is a glass aquarium to house - Skimmer + pump, reactors + pump, UV outlet, autodrip float, and bulkhead chamber for external main pump.