I experimented with using air stones and a bubbler that I bought at the local store because I was concerned with keeping my fish alive. It turned out that I did not need the bubbler, but it might be needed if the ecosystem is overcrowded—especially if you use aquatic plants inside the bottle, which photosynthesize during the day (supplying oxygen to the system) but not at night (when their biomass continues to respire and may consume so much oxygen that the fish cannot survive).