EHEIM SUBSTRATpro Enhanced biological filtration medium with optimal volume usage, long service life, and high degradation performance. SUBSTRATpro is made of spherical fused quartz sand. The spherical shape allows for high bulk density, meaning the full volume can be utilized in the filter (filter baskets or units). Additionally, the improved surface of the spheres ensures intensive stability of the important bacteria for water purification. A dense bacterial lawn is formed. The large number of bacteria also reduces nitrite peak loads and extends the filter material's lifespan. EHEIM SUBSTRATpro is suitable for both freshwater and saltwater, washable, and can be reused multiple times. Enhanced biological filtration medium made of fused quartz High bulk density due to spherical shape (balls) Very dense bacterial colonization Longer service life Better degradation of nitrite pollutants Can be reused multiple times (wash carefully for cleaning) Suitable for freshwater and saltwater Biological filtration media The main task of biological filter material is to provide the best conditions for bacterial cultures to grow, so a bacterial lawn develops after a short period. The bacteria feed on all types of dirt particles and convert substances that are critical for the aquarium. After initial cleaning with mechanical filter media (such as EHEIM MECH or MECHpro), biological filtration is the most important. It ensures clear, healthy water and stable water values. That's why we invested a lot of research into developing biological filter media. Tip: Never clean or replace the biological filter material completely at once (and never excessively). Bacterial cultures should not be completely destroyed, otherwise recolonization will be delayed. Filter baskets in external filters and filter units in Aquaball and Biopower internal filters are ideal for partial cleaning. Mechanically: No Biologically: Yes Absorptive: No Chemically: No Net bag: No Freshwater: Yes Saltwater: Yes Width: 140 mm Height: 177 mm Depth: 73 mm