Corrections: these are NOT “closed pens”, they are called “semi closed” (as called by the Canadian Government). Closed pens would mean that the circulating water does not flush back and forth, and would be on land, or a different actually fully closed system. These pens pump millions of gallons constantly in and out, with no water treatment of the dirty swimming water. The quick graphic also gives the false impression of a closed system, and does not show the huge water intake and output openings on the sides of each pen. Other wise well done 3 minute video
https://www.youtube.com/watch?v=wQvhrn9GY78
