Ceramic granule media Juwel bioCarb XL for Bioflow XL filter (8.0). Juwel Cirax Compact filter media is designed to allow water to flow freely and efficiently through your filters, while at the same time providing a large surface area for the growth of bacteria responsible for breaking down harmful ammonia and nitrite in the aquarium. Suitable for JUWEL Rio 400/450, Vision 450, and Trigon 350.