Hobby Grotto Lava are particularly beautifully structured unique pieces made of Icelandic foam lava. The stones can be glued with aquarium silicone to form mysterious caves or natural-looking back walls. The porous lava rock provides an ideal habitat for bacteria and microorganisms in the water. The grotto lava is also suitable for planting in your aquarium, because the rough surface provides support for plants and allows a stable structure.Hobby Grottoes Lava+ individual stones can be combined individually+ numerous design options, according to individual taste+ to create decorative and mysterious hiding places in freshwater+ can be glued with aquarium silicone