I have had problems with bleach.
I use H202 at about 35% or better. Soak over the level of the rock, let set for 30 min or so, stir the rock with a broom handle for about 5 min, rinse off with fresh water good and they are good to go.
Where I am at rock is a dollar a litre. That can get expensive when you are using 250-300 litres a whack!!!!!
I have got rock I have had 2 years with out adverse affects.Trash cans full.
You can release the nutrient lock with the H202 and water. After that a good soak and rinse and they are ready to go.
My .002
D