Fish lifespans can average anywhere from one year to 20 years. The lifespans of aquarium fish vary greatly depending on the species.
Usually, smaller fish have shorter lives. For example, bettas live for an average of two years, and killifish may only live for a year. On the other hand, larger fish lead longer lives. Loaches can live 10 years or longer. Goldfish vary in size depending on their habitat, but they can live for decades.
Most domestic fish do not live as long as they could. Improper care and poor environment usually lead to early death in many species. Although goldfish can live 20 years or longer, many fail to last a single year. Pet owners can increase the lifespans of their fish if they feed them properly and make sure their tanks stay clean. Tank size also plays an important role in lifespan. For example, goldfish do not do well in small tanks.