I did it many times .
Here is how I did it.
Put all rocks in a barrel and bleach them overnight.
Next day, rinse with water
submerse the rocks in new tab water for 1 day
Next, rinse the rocks
Next, submerse rocks in water with baking soda for 1 day
Next, rinse the rocks with tab water
Next, submerse the rocks in the bucket with clean tab water for a couple of days
Next, rinse the rocks, let it dry for 7 day
Final: start curing the rocks
Bleach the rocks sure will make the rocks very clean
After one day, rinse them