The above process is similar to the treatment of fresh fish in holding tanks on fishing vessels. Prior to the introduction of ozone, chilled brine was used to maintain the quality of the fish. This worked for up to about 5 days, after that time the fish was unmarketable. Since ozone has been implemented in fish holds, the fish can be now be held preserved as long as 21 days, and still be as good as if freshly caught. In reality, the actual time fish is held is always much less than 21 days as the fish is delivered to a processing plant or market. Three weeks has probably been the longest time tested. Once the fish processors in Norway saw the difference in the quality of the fish delivered, they demanded that all fish boats use ozone to maintain their catch. There is no more need to buy costly chemicals. Over the years, the use of ozone in this application proved to be superior to any other treatment.