Bacteria additives don’t just chew up the nitrate and phosphate in the typical saltwater aquarium, they consume oxygen too, and lots of it. If you dose any sort of product that feeds bacteria (such as biopellets, vodka, etc.) or adds bacteria directly to the system (BioDigest, ZEObak, etc.), then you will also need a healthy supply of oxygen. This can come from anywhere like a protein skimmer, air pump, or even just surface agitation with a powerhead. As the bacteria in the system grow, they take in oxygen at an increasing rate. If not taken care of, the dissolved oxygen (DO) levels can become depleted and the aquarium livestock can suffer. Regardless of the mechanism, the oxygen will need to be added to the aquarium to keep DO levels high enough to allow your fish, corals, and invertebrates to thrive.