Sorry about two posts, but here is what I do between grows. I sanitize all my pots/tools with bleach, I rinse really well to remove any left over bleach. For old soil I bake it in a low oven for a hour or two to sterilize it. If the soil is unopened I skip this step. I clean my grow room really well between grows as well to remove any plant debris and then I sanitize all surfaces including the walls with bleach water.