THE ROLE OF PLANTS IN AN AQUARIUM

Contrary to what is often thought, plants do not merely serve as decoration but also make a major contribution to the equilibrium of the aquarium (see page 196 on the mechanism of photosynthesis): by day, they absorb carbon dioxide (CO2) given off by fish and produce oxygen (O2). Moreover, they absorb nitrates, the end product of the nitrogen cycle (see page 19), and thus reduce the concentration in the water.

Plants are similarly useful for fish. Some species (like Ancistrus and Gyrinocheilus) feed on algae that grow on the decor, or even on fine-leafed plants (as in the case of livebearers from the Poeciliid family), though this can spoil the visual effect. Others, such as South American Characins, lay their eggs on the foliage, which helps to keep them out of sight of predators. Fish such as scaklares, watching over their eggs, use large leaves to fan them. When the fry are born, they find shelter in the vegetation - particularly plants with floating leaves - as well as nourishment there, as the plants enhance the development of microorganisms like infusorians, which are a valuable food source.

Finally, if the vegetation is sufficiently lush, it can also provide welcome shade and hiding places for adult fish.