Any part of your filter that is in contact with the water that is porous, or not a "hard" part, is going to host nitrifying bacteria. I wouldn't use any chemical on any of it. Rinse it in tank water. BTW, bleach can & will damage some plastic & rubber parts.
Eheim Pimp #204.
58 gal planted Oceanic
Red Turquiose Discus, Japonica shrimp, assorted Blue Eyed Rainbows, Tetras, Hatchets, Danios, Rasboras
10 gal low tech planted Celestial Pearl Danio (Celestichthys margaritatus) & Emerald Dwarf Rasbora (Microrasbora erythromicron)