New hobbyists who have had problems keeping fish alive for even a few months are always shocked to find out that the normal life span of the typical aquarium fish is measured not in months but in years. Although it varies from species to species, aquarium fish should live anywhere from three to seven years, or longer.

One of the three rules of fishkeeping is to not overfeed the fish. All uneaten food in a tank quickly pollutes the water. Overfeeding kills the fish with kindness. The best guideline is to feed only enough food each time for the to fish finish it within five minutes.

Diagnosing and treating aquarium fish diseases is so complex that entire books have been written on the subject. Fish can contract a great many illnesses, and curing them can take a great deal of knowledge and effort. In addition, preventing disease is almost always easier than curing it.