and high quality,Increase oxygen levels, lower CO2 and raise PH. It is an important instrument to successfully keep aquatic fish for respiration process. Durable, washable and sintered by high temperature. Creates bubbles in fish tank while attached to an pump( pump is not included). Creates water currents and dazzling underwater scenes. Color: Gray Material: Mineral Stone + Plastic Item Size: Approx. 40mm * 15mm (D * H) Item Weight: Approx. 30g / 1oz This stone is suitable for using in 30-60cm fish tanks. Suitable for inner diameter 4mm soft tube. Before , please immerse it in the water for 15 minutes. It it doesn't have bubbles in one part, please change the pump of higher . It will not work as normal if you attach to the submersible pump. Package Contents: 1 * Bubble Stone Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.