I wouldn't even do that bleach if there wasn't any disease. I would just rinse them in clean water and use. If you soak them in bleach too long it messes up the foam. Short period (5- 10 minutes) should be no problem.
I threw mine in the washing machine with a bit of bleach. Rinses and spins dry. Once dry you can dry and bleach dissipates or add some prime in a bucket and it will neutralize. When I had all the discus I rotated sponges between shipments . Even after cleaning they still got cycled pretty quick as always some good bacteria left