In Tank Carbon Filter for Tropical Fish Tank. comprising three printable components - case, tube and lid.
I have printed in white PLA and used this for several months with no ill affects to my fish or shrimp in my tank - but use at your own risk. The assembled filter is attached to the return tube from my EHEIM external filtration unit.
Print the lid base down, the case I printed with the nozzle section up with supports.
The parts should push-fit together and require no bonding. Install a thin layer of gauze inside the lid, fill the case with active carbon and assemble.
The author hasn't provided the model origin yet.