There will be plant matter and pathogen spores inside crevices that will not wash out, so you can boil it or bake it to disinfect that, or you can do it with bleach, if you don't want to take any chances like me ...

Peroxide bleach will work, and so will chlorine bleach (NaOCl). Others may whine about chlorine, but it will not persist, just soak/wash a few cycles with water to get most of the bleached residue and chloride out. Put them out in the sun to dry if you really want to speed up and be sure no bleaching power is left. I personally would use a as my disinfectant solution an overnight 180:1 ratio of tap water to bleach for the regular strength bleach which I think runs around 4.5% to 5% as bought from the supermarket. Washing would help remove undesirable residual salt buildup which might be present, whereas baking wouldn't take care of that.

New hydroton comes out of a hot kiln so it is already disinfected but usually has powder that rubs off when it is new. A soak and a rinse does the job for me. I don't like it getting silty on the bottom or into the pump but it can be used straight too if you don't mind it.

I guess it depends on what crop you're growing, how sensitive it is to disease, and the disease issues you're had in the past.

Make sure to get a colander; they make it much easier to wash hydroton. An overnight soak in a diluted peroxide mixture wouldn't hurt.