I change the sock as needed. Usually every 2-3 days. I just throw them in an old salt bucket until I'm ready to clean a bunch. Then I take them outside. Turn them inside out. Spray them off with a high pressure nozzle until they are white again. Reverse them and spray again. Then I wrong them out and put them in a soak of ROdi and chloramine,chlorine, and phosphate remover for a few hours. Then I ring them out again and let them hang to dry completely. Can take a few days to completely dry sometimes. Before I put a new one in a rinse it with ROdi again and replace. I spend about 25 minutes every two weeks cleaning them. My nitrates have dropped since I started using the socks over the mechanicals filter that came with the Red Sea 650.
Matt