The farm in Spain's Canary Islands would raise about a million octopuses annually for food, according to confidential documents seen by the BBC. This equates to around one million animals, with some 10-15 octopuses living in each cubic metre of tank, according to campaign group Compassion in World Farming (CiWF), which has studied the plans. Along with the welfare of the octopuses, CiWF has concerns around the wastewater produced by the farm, which would be pumped back into the sea