Substrat Pro consists of spherical sintered quartz. The spherical shape allows for a high bulk density, ensuring that the volume in the filter (filter baskets or modules) is fully utilized. Additionally, the optimized surface of the beads promotes an intense colonization of essential cleaning bacteria, resulting in a dense bacterial mat. The high number of bacteria also helps to better reduce nitrite spikes and extends the lifespan of the filter material. Substrat Pro is suitable for both freshwater and saltwater, is washable, and can be reused multiple times.

The primary function of the biological filter material is to provide optimal conditions for bacterial cultures, allowing for the rapid establishment of a bacterial mat. The bacteria feed on dirt particles of all kinds and convert critical substances for the aquarium. After the initial cleaning by mechanical filter media, biological filtration is the most important. It ensures clear, healthy water and stable water parameters.