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.