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How to clean and replace the Fluval FX4 impeller

The Fluval FX4 uses an impeller to pump water in and out of the canister filter. Since, it is the only moving part of this product, the motor needs to be cleaned every three months.

Eventually, the impeller will breakdown due to wear and tear, forcing you to replace it in order to continue using your FX4 filter.

You can check out this step-by-step guide at Aquarium Blueprints to see how you can clean and replace the FX4 motor.

1. To begin, make sure you unplug the filter from the power outlet.

2. Next, you need to drain water from the Fluval FX4 canister.

2. If you haven’t done so already, make sure that the “IN” valve and “OUT” Valve have been closed as the red dials should be set to be fully horizontal.

3. Afterwards, detach the valves from the “IN” and “OUT” openings at the top of the FX4.

4. You should also make sure that the utility valve at the bottom has been closed as its dial should be set in the fully vertical position.

5. After draining all the water from the canister filter, we recommend that you remove the filter media baskets.

6. You can then use a cross head screwdriver to unscrew the three screws holding the protruding motor unit at the bottom of the canister.

7. After removing the screws, pull the motor unit out of the FX4.

8. Next, pull the impeller from the impeller shaft of the motor unit.

9. The impeller should have the following four main parts:

  • Front Rubber Bushing
  • Impeller Assembly (which should have the magnet and impeller fan)
  • Ceramic Shaft
  • Rear Rubber Bushing

10. If the rear rubber bushing is stuck inside of the impeller shaft, then you can use a screwdriver to knock it loose and then remove it.

11. Take apart the impeller and then inspect the four main parts for any signs of damage. If you notice any unevenness, then you might want to replace it.

If the impeller was making strange noises before and/or you notice issues with the pump performance of the filter, then you should consider getting a new impeller unit as well. Fluval recommends that you replace this part once every year.

If you are looking for a replacement impeller, then you can pick up the Fluval FX4 Aquarium Canister Filter Maintenance Kit, which you can find on Amazon with this link. (#CommissionsEarned)

12. If the impeller appears to be fine, then you can use a cleaning cloth or brush to wipe off any buildup on the front rubber bushing, impeller assembly, ceramic shaft and rear rubber bushing.

13. We also recommend that you use a cleaning cloth or brush to clean the impeller shaft as well as the rest of the motor unit.

14. You should also clean the inner area where the FX4 canister is connected to the motor unit.

15. Once you are done cleaning, reassemble the impeller and then place it back into the impeller shaft. Make sure that the rear rubber bushing doesn’t get knock loose when you put the impeller back into place.

16. Next, you need to screw back in the motor unit to the FX4 canister filter.

17. After you re-installed the motor unit, you can reassemble the rest of the FX4 and pour at least 1.6 gallons or 6 liters of tank water into the canister.

18. Make sure that the reconnect and then set the red dials on the “IN” and “OUT” valves to a fully vertical position.

19. Finally, you can re-plug the FX4 back to a power outlet to turn it back on.

20. The filter will automatically add water and remove any excess air.

After a few minutes, the FX4 should be working normally again.

You can take a look at the official video walk-through of cleaning and replacing the impeller of the FX4 below: