It's actually amazing that fish can survive in an aquarium at all. Compared with their natural habitats -- from jungle streams to vast lakes -- even a relatively large aquarium is tiny.
An aquarium also has several built-in limitations that work against the health of its occupants. No matter how extravagant and no matter how carefully planned, any aquarium is an artificial environment.
Natural aquatic ecosystems are much more complicated than the aquatic environment of an aquarium. The biological processes in a body of water have been finely tuned over millennia to become a complex, living system.
This system includes weather patterns, geological and chemical processes, and countless interrelationships among plants, animals, and microorganisms. The lifeforms found in these systems have adapted to very specific conditions, and their ability to survive depends on their environment.
A closed system like an aquarium is a completely different thing. By definition, a closed system means that the environment consists solely of the tank and its contents. The natural processes that, in the wild, would provide food, protection, and a clean, uncontaminated environment for the fish are not a part of the aquarium.
As a fishkeeper, your primary responsibility is to see that these things are taken care of in the confines of your aquarium.
Providing nourishment and a safe and comfortable habitat are essential. Maintaining the water quality, however, is something a bit less obvious to most new aquarists.
Water quality refers to the amount of debris, pollutants, and other undesirable substances that appear in the water either naturally or through contamination, and more aquariums fail due to poor water quality than probably anything else.
Why is water quality so important? Approximately 80 to 90 percent of all fish diseases are due to physical stress. The most common source of stress is from living in polluted water.
This stress, if persistent and unrelieved, causes the immune system of a fish to become less and less able to fight infection from disease-causing organisms that are always present in the water. Some species of fish suffer from this problem more quickly than others, but all fish eventually become sick and die when kept in poor-quality water.
Beginning aquarists may have a difficult time keeping their aquariums healthy not because they lack skill or motivation but because they lack knowledge. Keeping water clean is actually not difficult at all; it requires only a little understanding, a little effort, and the right equipment.
Go to the next section to find out more about the importance of aquarium water quality.