Lifespan

[prussell]

I am a great believer in providing the optimum water chemistry for each species. I feel that it is only by providing the ideal conditions can we expect fish to live out their full maximum lifespans in captivity. That is why it troubles me whenever I see an aquarium containing both livebearers and tetras because if the chemistry is right for one, it must be wrong for the other.
There are plenty of sources of information that list the ideal water conditions for each species. However, the one bit of information never included is the normal lifespan. I tried keeping male Siamese fighters in my aquarium on several occasions but discovered that they usually died after nine months to a year whilst many of the other fish in the tank have been in my care five years plus. I concluded that I was failing to provide the conditions that they require. It was only after a casual conversation with one of the dealers I frequent did I discover that Siamese fighters are a short lived species and twelve months is a “good innings”. If there is someone out there with more knowledge than me that could band fish species as either ephemeral, potentially long lived or permanent guests, I for one would find it most useful.

[Carylnz]

If you Google this you will find some answers. Generally speaking, the bigger the fish the longer the lifespan.
Goldfish ought to live 35+ years. There is one recorded at 43 years.
Siamese Fighters about 18 months but remember they are usually adults by the time you buy them hence the 12 month or so lifespan once you get them home.
Apart from the fighters and some killifish, you ought to get 4+ years from small species up to 15+ for larger.
I have a friend with 7 clown loaches that are now in their late 20's.
The large cichlids, like oscars, 10 - 15 years. I had a male Ancistrus make it to 12 years.
There is a story about an arowana that lived over 60 years - passed down from grandfather to father to his son.

[prussell]

Many thanks, Carlynz. That is very helpful. When I kept a hard water aquarium with livebearers, I noticed that the females outlived males by a considerable margin; particularly so with guppies. I presume this is Mother Nature’s way of compensating for an uneven sex ratio in the progeny.

[Carylnz]

Lifespans depend very much on conditions;
water quality
Tank size
Temperature
Sex ratio
Stocking levels
Aquascape (places to get away from others etc)
How often they have fry. Females who are rested between spawnings will live longer than those constantly having fry.