Every other day, splash of bleach (Gentle cycle, hot wash/cold rinse). As mentioned, do NOT use detergent, fabric softener or anything like that. They'll be dry enough after spin cycle to naturally dry the rest of the way.
I haven't had a problem and for the last couple months I've been testing daily (vodka dosing). Our washer does have a 2nd rinse cycle option, but I don't use it.
I do have 5 socks and rotate them, so it's never right back in. But that's not terribly significant for this question.
havinng extra to rotate is a great idea. without bleach its hard to get them really clean, but its good enough with out if you are exchanging regularly.
I flip my filter socks inside out and then into the washing machine with hot water. I rotate between two socks every few days. Since I've used filter socks, my tank water is crystal clear but now my Kenmore has a horrible case of hair algae.
