Fish Tank Filter Size M

M filter Cartridge - Use "Blue Bonded Filter Pads" cheap from your local pet store - the ones that have 2 distinct materials white side and blue side so it can be easily pulled apart, lay the white side on the "back part.. Tabs up" then add some activated carbon... carefully line up holes with the top part and lightly tap together with hammer and cut excess filter fabric...

Keep in mind the tabs are very fragile, this is version 2, improvements include; reduction in material and print time