A CUSTOM-DESIGNED air processing system already being used in Canada is to be trialled in Scotland to deal with plankton which is potentially harmful to farmed salmon. Scottish Sea Farms is to test the greener system, Flowpressor, to protect its salmon from what it called a major threat to the health of farmed fish worldwide. Many species and concentration of plankton are vital to a healthy ecosystem, but others can harm humans and animals. In the case of farmed salmon they can cause damage to the gills and deprive the fish of oxygen. Aeration is the process of pumping air into salmon pens to boost water movement and quality, and is one of several protective measures taken by salmon farmers when rising levels of plankton are detected during daily water monitoring.