Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
A little bleach will also kill pretty much everything in the sand, then rinse with some dechlor in the water, then dry it, especially in the sun. Any chlorine remaining after the dechlor rinse will evaporate.
As weak as 19 parts water: 1 part bleach is a weak solution that some plants can tolerate, but kills quite a lot of algae, but a stronger solution would be quite safe for sand, and more sure of killing things. Let it soak a while (half an hour or longer).