How Long Should My Fish Live?

I set up my 200-litre (44 gal) aquarium four years ago and I still have some of the original fish – five out of the six corydoras, three penguin tetras and two diamond tetras (looking a bit ragged these days but still feeding well).

It got me thinking about lifespans of fish. How long is the average lifespan of some of the common fish we keep if they are properly cared for? 

BRIAN GUTHRIE

Neale Monks Provides an Estimate of Fish Lifespans

With good care, most small tropical community fish live between two and five years, medium-sized species such as angelfish and gouramis around five to ten years, while some catfish and goldfish can live for decades. However, this isn't a hard-and-fast rule, though. Many factors influence how long a fish will live

Fish Lifespans and Temperature

This is a topic that has been much discussed over the years, but inevitably the actual science is somewhat complicated. Fish lifespans are highly dependent on ambient temperature: being cold-blooded animals, their metabolic rate will be much higher at tropical temperatures than coldwater ones.

All photos by Shutterstock

Very approximately, increasing temperature by 10°C (18°F) results in metabolic rate doubling. If you imagine something like a goldfish kept at 25°C (77°F), its metabolism will generally run faster, which often results in faster growth than one kept at, say, 15°C (59°F) provided other conditions are suitable as well.

Since the one kept at a lower temperature is growing more slowly, it’ll also reach sexual maturity more slowly and likely live for much longer as well. A properly looked after goldfish can live at least 15 years. 

Wild and Captive Fish

In the wild, fish are exposed to a range of selection pressures that favour lots of different genetic traits, including foraging behaviour and physical fitness. The fish has to carefully balance finding a mate while hiding from predators on the one hand (or fin), while on the other, it needs to spend enough time looking for food so that it doesn’t starve.

In captivity, though, the situation is entirely different. Food appears out of thin air on a regular basis, there are no predators, and if a potential mate is in the tank, it won’t be hard to find. 

Conditions in captivity are usually quite benign compared to the wild, not just in terms of the absence of predators, but also things like more stable temperatures and the lack of a dry season that might cause streams or ponds to dry up completely. Very small fish such as neons and guppies are probably lucky to live a year in the wild, but in captivity frequently live for 2-5 years.

Even medium-sized fish like gouramis and angelfish probably don’t live very much longer in its natural environment, with mortality of juveniles especially, being incredibly high. A five-year-old angelfish in the wild would be doing very well and likely has some excellent genes if it’s escaped predators and avoided starvation for so long. By contrast, plenty of domesticated angels live for ten years or more, not because they’re genetically ‘better’ than their wild relatives but simply because they’re living easier lives.

It is worth keeping in mind that some selectively bred fish can end up with poor genetics from inbreeding, and this can reduce their lifespan. 

So, What Age Should My Fish Reach?

Small fish, Neon tetras, lambchop rasboras and zebra danios should live something like 2-5 years, but as we’ve seen, temperature matters, so if you keep your neons or danios warmer than they actually like, they won’t live as long.

Medium-sized fish, like angelfish and three-spot gouramis should live around 5-10 years, possibly more.

Catfish tend to be quite long-lived even by fish standards, with the common plec species (typically Pterygoplichthys and Hypostomus spp.) easily living 20 years or more when properly kept.

Many killifish, on the other hand, have evolved to live fast and die young. Many annual killifish species usually don't live for much longer than a year, even in captivity.

Without wanting to jinx it, my Panaque nigrolineatus, Clarabelle, was purchased in 1996 and is still doing well, and given her size when purchased, must be over 30 years old by now.

So, remember, buying a fish can be a long term commitment!