I turn mine inside out, rinse them out well in the laundry tub first - get as much gunk off of them as possible. Then run them on the Whites cycle with bleach - no soap, no softener. After that cycle is done, I run them through a cold water cycle - no soap, no softener, no bleach - as an extra rinse.
They then air dry for several days. I also throw my half dozen "aquarium only" towels in there at the same time.