The use of Sera Rock Black Lava in the aquarium creates a natural and special look. The dark stones provide a beautiful contrast to the plants and fish in the aquarium so that their colors become even more intense. They also serve as hideaways and shelter for shy or territorial fish. This reduces stress and therefore contributes to a healthy and appropriate keeping of the animals in the long term. Lava rock also has functional benefits. The porous structure of the rock allows the settling of filter bacteria, which ensure the biodegradation of pollutants in the water.sera Rock Black Lava+ particularly porous deep black lava rock for setting up aquariums+ the unique structure allows the combination with epiphytic plants such as Java fern or Bucephalandra+ useful filter bacteria are provided with ideal settling areas on and in the stones+ particularly suited for creating complex structures and natural hideaways for fish+ available in two different sizes:+ L 16-23 cm+ XXL 27-35 cm+ Image s