Some billionaires exercise their philanthropic bent by building museums or symphony halls. The legacy of Bernard Marcus, who runs an American DIY chain, will be the world's largest fish tank, almost 10 times the size of the London Aquarium. The Georgia Aquarium, due to open in Atlanta in November, will have 5m gallons of water (almost 19m litres) and more than 100,000 fish. It will be home to two white beluga whales, giant groupers and octopuses. The main attraction will be two whale sharks, the world's largest fish, which can grow to more than 40 feet. The sharks, Ralph and...