What type of fish do you have and how old is your oldest. I have a yellow tang that has been with 3 owners and is estimated at 5 +/- a year. I have had him for 7 months.
6 year old Female maroon clown. Used to be a male. The original female passed away last year. I have a 5 year old dogface puffer and zebra moray eel. I've been in the hobby 6 years, so...
I used to help take care of a Stichodactyla mertensii anemone that had been in captivity for 18 years! 8O
Had a hippo tang for 9 years now. Bought "Dory" when she was the size of my thumbnail! She has been through thick and thin...got me through the "learning" stage and is fat and happy!
I have a tomato clown that is at least 9 yrs. old and some damn damsel that is 6 years old. I hate that damsel and so does every fish in my tank.
How do we really know how old any of our fish are? The question should be how long have they been in our tanks other then that age is a guess is it not?
I purchased a snowflake moray 11 years ago when he was already 18". He lived with me for 10 years before passing away from what I believe was old age (no symptoms or problems). He was 30" when he died, which is their max. size. So he had to be AT LEAST 13 years old, maybe more.
I have a striped Raphael catfish that is around 7 years old, it survived a 3 day power outage in Edinboro, PA...lake effect snow central and kicks it with my freshies. As for marine I had a Huma Huma trigger live 4 years.
yellow tang since 10/00, so over five years now.
pink psuedochromis for 6.5 years,
in a previous tank/life, a pair of ocellaris that between me and a subsequent adoptee went 10 plus years.