When trying to start up your Fluval FX4 or FX6, your canister filter may not be priming properly. To see how you can fix this problem, you can check out this troubleshooting guide at Aquarium Blueprints.
1. The first step you can take is to disconnect your canister from the power outlet. You can then plug it back again to see if the priming will automatically start. If not, you can try using another power outlet.
For the uninformed, the FX4 and FX6 should start pumping in water for 1 minute to fill the canister and then stop for 2 minutes to remove air. Afterwards, the filter should work normally pumping water in and out of the canister.
It should also be noted that the FX4 and FX6 will stop for 1 minute after every 12 hours to remove any air from the canister.
2. If the priming is taking longer than expected or not working at all, then you should make sure that the FX4 or FX6 is set up properly.
For best results, the canister should be placed between a range of 20 cm to 150 cm below the water surface of your aquarium. The water line should also be no more than the 20 cm from the top of the fish tank.
Furthermore, you should make sure that the hosing is connected straight to the canister. There should be very little bending.
3. You should also make sure that the IN and OUT Valves are completely opened. The red dials of these should be completely vertical.
4. Moreover, Fluval recommends that you place the output nozzle to above the water line before you start the priming process.
Otherwise, water and air could easily fall back into your FX4 or FX6 canister, causing potential issues.
5. Before planning your canister filter back into the power outlet, you should make sure that you have enough water inside your canister.
Fluval recommends that you add 1.6 gallons (or 6 liters) of tank water in your FX4. If you have a FX6, you need to add 2 gallons (or 8 liters) of tank water.
Once you have enough water, plug the canister filter into a power outlet and then check if the priming process will start.
6. The priming issues could also be related to clogging.
To prevent your canister from being clogged, make sure you rinse the filter media to remove the organic wastes.
When rising, you should be using tank water you plan on throwing away during a water change. Tap water contains chlorine and chloramine, which will harm the beneficial bacteria living in your filter media unless you use a dechlorinator.
If the sponges or foams look extremely dirty even after a thorough rinsing, then you should replace them.
7. The hosing can also get clogged up overtime as the organic wastes will build up within the inner walls.
To clean the hosing, you can use a faucet or hose to run high-pressure water through them to flush out the wastes.
8. Your priming issues could also be related to the impeller as it is the only moving part of the FX4 and FX6 needed to help with water circulation.
If you don’t clean the impeller, then it will slow and eventually break down. Even with proper maintenance, this part will eventually malfunction.
To see how you can clean and replace the impeller for the FX4 you can check out this post. For the FX6 impeller, you can take a look at this article.