Dennerle quartz gravel is a classic in the range � for many decades one of the best gravels you can use in your aquarium. The excellent appearance and perfect biological function of the gravel, which does not harden the water, are probably unique in this combination. It is lightfast and CO2 resistant, can be used again and again, and retains its color even after years. Due to the iron oxide coloring, the quartz gravel is water neutral and guaranteed free of pollutants. The grain size of 1 � 2 mm suits bottom-dwelling fish and reduces the risk of dirt in the gaps.