Aqua-Flow XL Biological internal filter The ideal internal filter for tropical or cold-water aquariums. The large filter volume with Bio Action cartridge ensures optimum biological filtration of the aquarium water in three steps: Step 1 Fully open structure filter foam for perfect mechanical filtration. Step 2 Active carbon removes organic contamination, chemicals and dyes from the water. Step 3 Crystal-Max, a very porous filter medium, it acts as a sponge for micro-organisms. Waste products and harmful substances are decomposed very effectively. The Easy Clean click system makes filter cleaning easy, you can clean or replace the filter media every month in almost no time. Extensive manual included!