Lucky Reptile Humus Brick consists of natural coco peat which has been pressed to a tight brick. If placed in water, this terrarium humus will swell up to about 8-10 times its volume. - Excellent for burrowing animals and can be used either dry or humid. - An excellent substrate for tropical lizards, frogs and tarantulas. - A natural product (100% bio degradable) and free of chemicals, pesticides or fertilizers. 1kg brick expands to about 8 litres of terrarium substrate.