Fish Under Stress: Not only human beings, but also fish suffer from stress. Aquarium fish, especially, can be exposed to many kinds of stress. The cause usually is environmental.

Stress factors for fish in an aquarium are: frequent fluctuations in water temperature, water chemistry, chemical substances (fertilizer, medications), polluted water, crowding, water saturated with excrement, improper diet, transfers, moving, aand overly strong water circulation. Frequent handling, netting, or even your own rapid movement by the tank can trigger anxiety. lntraspecific fighting for a place in the pecking order means intense stress for the inferior fish if the tank is too small and hiding refuges too few. Extreme stress can lead to shock and death of the fish.

Fish are often exposed to stress from substances in the water. For a certain period of time a fish can maintain its body equilibrium by adapting to the changing factors. When this is no longer possible, a state of exhaustion sets in, ending in death. Stress will directly weaken resistance to infections. The result is often an outbreak of disease caused by latent stages of parasites or by organisms in the aquarium. Overpopulation severely stresses the inhabitants of the aquarium. Even with good filtration, the water is increasingly polluted with the accumulation of wastes. The fish get in each other's way lacking sufficient places to hide. A guideline for the optimal population of a tank is often quoted as five liters of water per fish (1 liter=1.06 quart). Therefore, a 100-liter aquarium can house 20 fish. Large or small fish? This kind of calculation leaves something to be desired.

When setting up a tank with young fish, the calculation should be based upon the anticipated adult length. With these guidelines, a good filtering system, and regular changes of water, metabolic wastes will not seriously burden the water, unless you systematically overfeed. Beware of those aquarium fish foods that claim "doesn't cloud the water." All foods cloud the water if uneaten, and most foods cloud the water after they've been eaten if the fish don't digest them. If your tank gets cloudy, change the fish food and feed less.

Prevention of Diseases: To keep fish in an aquarium healthy and to provide for their long life, the guidelines of this article must be taken to heart so as to prevent disease and, avoiding introduction of diseases. Therefore, new arrivals should be quarantined before introduction into the aquarium. Use several catch-nets, ideally a separate one for each tank. A bucketful of concentrated disinfectant solution serves for the sterilization of used nets and other items that come into contact with aquarium water.

These items should be kept from the bucketful of disinfectant except when being used, but they must be rinsed off in clean water before use. Neither these items or your hands should be taken out of one tank and dipped into another tank without first disinfecting them and then rinsing them. This cuts down on the transmission of disease organisms from one tank to another.

Plants that were not grown or kept in fishfree tanks can bring parasites into the aquarium. As a rule, plants from nurseries can be considered free of disease-causing organisms. Plants that were in contact with fish can be disinfected in an alum solution.

In summary, it should be noted that the successful prevention of disease depends to a large extent upon how maintenance is carried out and all precautionary measures are adhered to. Regular water changes are obligatory. It is better to do it often with a little water than infrequently with a lot of water. Support the biological self-cleansing processes in the water by providing active biological filtration. The fish that lives under healthy conditions is in a better position to resist even the more aggressive parasites.