A major Tokyo aquarium has lost almost all of the fish inside its largest tank, likely due to lack of oxygen.
Sunshine Aquarium resumed public display of the tank on Thursday after suspending some operations the day before and announcing that a total of 1,235 fish, accounting for 94 per cent of the fish in the massive Sunshine Lagoon tank, had died.
The mass death occurred after the aquarium stopped a bubble-producing cleaning device for the tank to enhance the effectiveness of chemicals added to the water to treat some unhealthy fish.
It continued to supply oxygen to the tank through another device and had spotted nothing abnormal by Tuesday evening, but a security guard noticed many dead fish the next morning, it said.
Only 73 fish of 23 kinds survived, according to the operator.
The fish tank is 12 metres in length, 9.6 metres in width and 2.4 metres in height and is capable of holding roughly 240 tonnes of water.