"I had read to buy playground sand at a hardware store for my hermit crabs, so I did. It was awful !!! It had gotten wet & mildewed. It was so strong that it made my daughter's bedroom smell mildewed. That money & time was wasted. When I bought the "Hermit Crab Calci-Sand" it might have been a little more expensive but it was WELL worth it !!! It was in perfect condition when it arrived & the crabs seem to love it !!!! They've even started burrowing more !!!!"