Many freshwater fish average about 1 to 3 years of life. Some of the more popular species with this short lifespan include fantail guppies, swordtail platy, mollies, rainbow fish, hatchet fish, corydoras catfish, some cichlids, rasboras and tiger barbs.
There are also several types of fish that live around 3 to 5 years with proper care and feeding. These fish include betas, kissing gourami, zebra danios and Jack Dempsey.
If you are looking for a fish that will be around for up to 10 years, think about neon tetras, angelfish, Oscars, and plecostomus.
The longest lived of all the popular freshwater fish is the goldfish. If provided proper feeding and a clean, healthy environment, these fish can live up to 15 years. The oldest reported goldfish actually lived into his 30s.
Saltwater fish tend to be more difficult to keep in captivity but if you provide them with the best possible environment (perfect water quality, excellent diet and appropriate tank size) some saltwater fish can live for many years. Most published information about the lifespan of saltwater fish is from public aquariums where the fish are kept in the best possible conditions. Many saltwater fish succumb to illness early in life due to poor husbandry.
Some saltwater species only live an average of 2 to 4 years. These include butterflyfish, mandarins, Moorish idols, gobies, blennies, wrasses, damselfish, squirrelfish, triggerfish, surgeonfish, and tangs. Most small tropical seahorses that are available for aquariums live about 3 to 4 years. The larger seahorses can live longer but are rarely available for the home aquarium.
A few of the more hardy species can live up to and over 10 years, including lionfish, clownfish, eels, and groupers. There are many varieties of angelfish and some can live quite a long time. The Queen angelfish, French angelfish, and gray angelfish can live up to 20 years but grow to a large adult size. For this reason, few mature adult angelfish are kept in captivity for as long as 20 years.