Rock Cave 3 This rock cave (3) is made of high quality polyster resin gives a high decorative value to the aquarium. Completely free of toxins and neutral for the water values, it fits well among the other decorations and aquarium plants in the aquarium. The Rock Grotto (3) by Aqua Della can optionally be decorated with small mosses to make it even more natural. Shrimp, crayfish and fish can find an excellent hiding place through the openings. All Aqua Della aquarium decorations are made of 100% polyester resin. This is absolutely toxin-free and does not affect the biological balance of your aquarium. This means that the aquarium deco never releases substances into the water and does not affect the water values. Suitable for both fresh and salt water.