Professional Filter Bio Rings Media For Canister Filters, Refugiums, Wet/Dry & Sump filters, Substrate or Mechanical filters! Sintered quartz, Each Box Is 16 OZ (453 grams) 1 Box of Professional Filter Bio Rings Media for canister filters, refugium & sump filters, substrate or mechanical filters! Sintered quartz, Each Box Is 16 OZ (453 grams) Super-Porus quartz material provides superior biological filtration with added surface area for beneficial bacteria growth Long-Lasting durable and reusable. Unique shape promotes consistent water flow while trapping large debris Bio-Rings media should be used as a middle stage of filtration. Replenish a quarter to half of the Bio Rings at a time to allow for proper seeding of new Bio Rings media. Does not affect water characteristics The Aquarium Masters Bio Rings filter media are made of inert ceramic rings that are capable of supporting large populations of water purifying bacteria. Consider adding the other Aquarium Masters and Blue Spotted products to your system: cut-to-fit carbon reducer pads, phosphate reducer pads, nitrate remover pads, dual bonded poly pads, activated carbon, sumps, thermometers, submersible heaters, airline tubing, air stones, betta log, betta leaf, & fish nets