100% natural substrate. Ideal for natural terrarium set-ups. Increases humidity in terrariums. Nutritional substrate for live plants. Instructions: Place the brick in a pail/bucket or sink. Add 3-4 liters of water. Allow the brick to expand for 20-30 minutes. Wring out excess moisture. For small animals, snakes and tarantulas, lay out moist substrate in the sun to dry before moving to your animals's enclosure.