This will work for all aquarium equipment, including sponge filters and nets:
Dilute regular household bleach (no detergents or fragrances added) 1 part to 9 parts warm water. Soak for 15 minutes and rinse with water. Rinse again. Rinse, rinse, rinse, rinse, rinse. Rinse one more time. (Actually, I just throw the stuff in the tub and let the shower run on it for about half an hour while I do something else.) If you want to use the disinfected item immediately, rinse it off one final time in water + dechlorinator. Otherwise, allow it to air dry, and the chlorine will decompose and evaporate. i hang all of my nets on hooks and they air dry perfectly... never just lay them down somewhere..i also try and have a good number of nets of various sizes to avoid as much as possible the constant use of one in to all the tanks..