Stress
An important key in avoiding potential health problems among aquarium animals is to understand the role that stress plays in this area. An animal that is under stress will succumb to disease or parasites much more rapidly than will a well-adjusted individual. A wide variety of parasites are nearly always present in the captive environment and they are quick to take advantage of immune systems weakened by stress. A healthy animal might be able to tolerate suboptimal captive conditions, while a stressed one of the same species might be killed by the very same circumstances.
All animals employ a variety of chemicals that enable them to deal with stressful conditions. This process is often referred to as the “flight or fight reaction,” in that adrenaline and other substances prepare the animal to defend itself or to escape from a situation. This reaction is a necessary survival tool in the wild. In captivity, however, what often happens is that environmental stressors persist for unnaturally long periods of time, and the animal is unable to escape from them. The bodies of most animals are not designed to withstand long-term exposure to stress-induced chemicals. Over time, the immune system will be weakened, and the fish or invertebrate will readily succumb to disease or parasitic infection.
Factors that cause stress to aquarium animals may arise from any number of conditions that originate outside of the animal itself. The most common stress-inducing factors are poor water quality, improper diet, aggressive or threatening tank mates, and a captive habitat that does not meet the animal's needs.
The animals that you purchase will almost certainly have experienced a range of stress causing conditions in their transit through various stops along the way to your home. Wild caught animals, particularly those from distant locales, may have had an especially difficult journey. You should, therefore, take care in establishing and observing newly purchased pets.
One of the most effective ways of eliminating stress from your pet's life is to learn as much as you can about its biology, diet, methods of reproduction, and natural habitat. You will then be able to provide captive conditions that are conducive to natural behavior and good health. Read widely and learn from others whenever possible.
Your aquarium must be designed to meet the environmental needs of your pets. Many animals are extremely specific in their requirements and will fail to thrive if they are not given a close approximation of their natural habitat. For example, retiring animals such as octopus require shelters, active bottom dwellers such as stingrays require expanses of flat, sandy areas, and large, surface dwelling fish such as arawona need to swim unencumbered. Providing suitable hiding places and densely planted aquariums for shy animals will enable them to live in comfort and to exhibit their natural behaviors.
It is very important to keep your pets in an environment that provides them with proper temperatures and appropriate levels of salinity and pH. Even if an animal survives under conditions that are not to its liking, its immune system will certainly be weakened, and this may prevent the animal from fighting off disease and parasites. You must also be careful to avoid rapid fluctuations in water quality parameters. This can best be accomplished by regularly monitoring nitrates, ammonia and pH levels, and by installing a backup aquarium heater, so that temperatures will not plummet if your main heater fails.
The animals with which your pet shares the aquarium have an important effect on its overall health. Aggressive individuals may prevent others from feeding properly or may attack more passive creatures outright. Even in the absence of actual hostilities, a dominant animal can be a significant source of stress to others in the aquarium. The mere presence of a potentially aggressive individual can trigger stress reactions in others that will, in the long run, compromise their health. Even creatures that normally live together in the wild may not coexist within the confines of an aquarium. It is also important to ascertain that the animals are compatible in terms of their activity patterns. Shy, retiring creatures may be disturbed by actively swimming tank mates, even if there is no actual aggression between them. Likewise, nocturnal animals such as catfish may become very active at night and disturb diurnal species.
Unfortunately, we know little about the nutrients required by many commonly kept fish and invertebrates, especially marine species. An inappropriate or incomplete diet is one of the most common long term stresses that aquarium animals are forced to endure. Over time, even individuals that feed vigorously and appear well will weaken if essential nutrients are missing from their diets. You should, therefore, learn all that you can about the nutritional requirements of the animals that you keep. Do not attempt to keep animals that, while interesting and desirable, require foods that you may not be able to provide.
