Lava rock is of volcanic origin, featuring a porous texture, making it very lightweight and versatile. This product is smoothed to form into oval or round shapes to appear as river stones. It can be used in a varity of aquairum designs including a Golf fish tank. Its comparably low weight, it is possible to create large structures with it. Lava rocks does not increase the hardness of the tank water. Weight: 13.5-15.5 KG, Approx. 48pcs. **Product images are for illustrative purposes only and may differ from the actual product. Due to differences in monitors, colors of products may also appear different to those shown on the site**