For 50 years, fishkeeping enthusiasts have looked to the Tetra name for products and solutions that add ease and beauty to their home. Whether you're an experienced hobbyist or just starting out, Tetra has everything you need–-from a large variety of quality fish food and innovative equipment to test kits and decor. Tetrafauna ReptoFilter Cartridges are disposable filter cartridges full assembled and ready to use. The filter cartridges use dense, dual-sided mesh to catch debris and waste while the Ultra-activated carbon absorbs odors and discoloration. Whisper filtration technology keeps your water crystal clear while removing odor and discoloration. Each cartridge is filled with Ultra Activated carbon which absorbs odors and discoloration. These convenient, pre-assembled and easy to use. The medium cartridges fit 90 GPH, 10i filter, decorative reptofilter and viquarium filters. For optimal water quality, change cartridge every 28 days (or sooner if water begins to back flow over the filter cartridge, a sign of a clogged cartridge).