[Placing filter materials in fish tanks and ponds can filter and purify water sources improve aquarium water quality stabilize pH and naturally clarify your water biofilters are good interaction and gas exchange between air and water. Grow healthy with these biospheres. And create a good living environment for the fish Aquarium filter coral stones contain natural ingredients. Please clean before use. It is best to clean with water from the fish tank or - water Aquarium filter coral stones can be used as a fish tank pond filter medium aquarium filter medium suitable for aquarium filters such as hanging filters and water tanks Aquarium filter materials can help absorb unwanted substances and increase oxygen in the water to maintain ideal water quality conditions]