Though the average specimen in captivity might live 25 or 35 years, an old koi named Hanako, from Mino province in Japan, has been shown to be over 215 years old based on analysis of her scales, and other 100+ year old fish are known from the same pond. Koi, like wild carp, can grow to 36 or more under perfect conditions.
The gold and silver medals weigh 412 grams (0.9 pounds) and the bronze medal weighs 357 grams (0.78 pounds). They are the biggest and heaviest summer Olympic medals ever made.
Since gold is expensive (duh) and making a substantially-weighted pure-gold medal for all 98 winners at the Winter Olympics would cost more than $2 million, a combination of metals is used to create Sochi golds. (Then again, if the Games really cost $50 billion, shelling out a few million for pure gold medals would have been a write-off.)