@Jeremy Lain I have no clue how old the oldest tang is, but I'll regurgitate part of an old thread on one of mine for many years which was discussed in another thread some time back.
Ultimately the answer would be 2005 to present time and in her new 14,000g display she can easily live 2o more years give or take a few. This is one of mine. I cannot answer your direct question, only IME. Sorry.
'In 2005 I had a friend who owned an LFS. He called and asked if I had an aggressive tank running. I had a 125 FOWLR for some fisty ones. Eel, a couple of triggers, yadda yadda.
So I get to LFS and h my friend was 'you gotta take this fish she has killed ~a dozen fishes the day he got her in. I was expecting to see some monster and it was an Atlantic Doctorfish about the size of a silver dollar. I laughed and took her home. Did QT then added to the 125g. She was the boss but didn't kill anything.
As she grew I kept buying larger tanks, a 225, and ultimately an 8' 300g. I really loved her. Anyway, she grew to 16 inches and a flick of the tail she was at the other side of the 8 foot and I knew she had outgrown it. She was very loving to me and got upset if my hand was in the 300g and I didn't pet her. She could have bitten the end of my finger off but would gently nibble on my arm or hand until I would pet her. I would come home and she was like a puppy waiting and always got excited.
It was breaking my heart knowing I was confining her to a 300g. I used to volunteer at http://www.ncaquariums.com/fort-fisher cleaning the inside of the larger tanks for sharks and such and called one of my contacts. They generally don't take fishes from folks but said they would take mine. Four years ago I transported her there and she resides in a 14,000DT with other Doctorfish. I go see her often as we go to Kure Beach frequently and she comes to the glass and looks at me every time. Crazy but true.
The pics are in the 300g I was running up to 3 years ago.
***The very last photo shown is at the aquarium from a couple of months ago coming to see me.
Thanks for the thread and allowing some great memories.'