If you're not paying attention, you may just overlook the most spectacular attraction at the Mirage. Most people first catch a glimpse during check-in, but others make a special trip just to see. It's a super huge 20,000-gallon saltwater tank behind the front desk and with an indoor coral reef that is home to more than 450 fish! The tank is home to exotic fish from more than 85 species including angelfish, puffer fish, tangs and other exotic sea creatures. These fish were specifically selected for their adaptability to the environment and compatibility with other species.