Replacing consumed oxygen by blowing a stream of very fine air bubbles
through the aquarium water is frequently necessary in aquariums, where
plants receive insufficient light or are not thriving, where the air
surface is small (depth greater than width), where crowding is
necessary, etc. Even in healthy aquariums, where plants are thriving,
conditions will be improved by an hour or two of aeration daily. Many
types of aerators are available.