Premium research-grade low-ash Fluval Carbon is highly porous, providing large amounts of surface area for adsorbtion of impurities. Fluval Carbon does not raise phosphate levels. Fluval Filter Carbon.
Fluval U3 Aquarium Filter BUNDLE. For the Fluval U3 Underwater Filter. Custom-sized, it fits perfectly inside the filter chamber to prevent debris bypass. The foam pad has a pore size that allows efficient water flow, less clogging and long-lasting filtration.