As with most large fish Black sharks can live for 20 years or more.
To back up the meanness reports i had to sell my 12" black shark as it was picking on my snakeheads and bichirs!!!!
Mine was fed mainly on a diet of meaty frozen foods and catfish pellets though it would sometimes nibble on courgette/cucumber and algea wafers placed in the tank for plecs.
now then vip dont no exact hoe long they live for but this one is nearly 17 years old and i no that for a fact i have grown up with it and its in perfect nick