Fish Tank Negative Pressure Filter (with Fish Toilet and Sedimentation Tank)

A negative-pressure filter tank for aquariums. Please wrap all threaded connections with PTFE tape. Several areas require adhesive bonding with 502 glue (or other glass adhesive) for secure attachment, as illustrated in the images.

Filter tank operational principle: The water pump is connected to the outlet to draw water (creating negative pressure). Aquarium water enters through the inlet; the angle induces rotation (we suggest adding several 1cm diameter plastic balls to enhance rotation, such as K1 filter media). The filter screen blocks larger waste particles, allowing those smaller than 1mm to pass; larger particles, due to rotation, gradually settle into the sedimentation chamber. Once inside, a recessed one-way channel and air layer prevent them from re-entering the filter screen. Smaller waste particles, after passing through the filter screen, are also drawn into a vortex by the rotating outlet, reaching the physical filtration layer (filter cotton), followed by the biological layer, and finally exiting the water flow.

For first-time users of negative-pressure filter tanks, remember the siphon principle: pre-fill the tank with water. A simple method is to connect both inlet and outlet pipes vertically and level, then pour water into one pipe until both water levels are equal. Connect the pump to the outlet and immediately place the inlet into the aquarium.

Remember the drain valve; we recommend connecting a hose with a valve, widely available online, for convenient periodic waste removal.

Note: This project utilizes negative pressure to minimize the risk of flooding. FDM printing has inherent limitations with liquids, therefore, do not reverse the pump connections to create positive pressure filtration.