'Picar3D aquarium filter pipes' are probably one of the best 3D-printed bio-filter mediums available on Thingiverse today.
The filter pipes are a fully biological filter material for all internal, external and trickle filter systems and are an excellent choice for small filters.
The 3D printed filter pipes provides anaerobic bacteria an extremely large amount of different open-pored tunnel structures. This allows an ideal supply of the anaerobic bacteria with nutrients and a smallest amount of fresh water.
There are oxygen-poor conditions within the tunnels. This makes the bacteria crack nitrate to get enough oxygen. Consequently, they continuously break down nitrate, and the aquarium water remains low in nitrate.
-Pre-filter with fibre-wool to prevent large particles from entering the bio-filter.
Your fishes will be more happy than ever!
-Some pipes are more difficult to print then others-