Juwel BioPlus Filter Sponge Coarse is a high-quality coarse-pored biological filter sponge designed for use in the Juwel Bioflow internal filter system. The coarse-pored structure provides effective mechanical filtration while also offering an ideal environment for beneficial aerobic bacteria to colonise, supporting the biological filtration process and contributing to stable and healthy aquarium water chemistry. Working alongside the fine sponge and other Bioflow filter media, the BioPlus Coarse Sponge is a key component of the Bioflow multi-stage filtration system. Easy to remove and replace, the coarse sponge should be replaced approximately every three months. Available in Medium, Large, and XLarge sizes to suit the full range of Juwel Bioflow filter systems. Note: Never replace all blue filter sponges at the same time to preserve beneficial bacteria colonies.