Filter socks, and front-end-loader washing machine ??

[wickedfrags]

Try a the Heavy Wash cycle, with a warm water wash and warm water rinse and this should get them clean.

I would not recommend the use of bleach at all given the amount of time and money we spend trying to keep chlorine out of our tanks. I have managed to get my filter socks clean for over 3 years without bleach. I imagine bleach is also harder on the filter socks themselves. I have never repalced a filter sock to date.