From 1954 to 1964 the largest aquarium tank in the world was at ‘Marineland of the Pacific’, in California, containing 640,000 gallons. Then, in 1964 an aquatarium opened in Tampa, Florida, with a tank containing 1,244,000 gallons.
But, the biggest tank of all was at Enoshima Marineland in Japan. It opened ca. 1965 with a tank nearly the size of a football field – measuring 200 ft. long by 100 ft. wide and 28 ft. deep – a capacity of over 4,000,000 gallons! It was built mostly in-ground to prevent it from bowing in the center. Some time in the 1970s, the original tank was demolished and replaced with a newer amphitheater-style pool.