Aqua One Nautilus & Ocellaris Canister Filter Troubleshooting Guide

If your Aqua One Nautilus or Ocellaris canister filter has stopped working, is making unusual noises, will not prime, or has reduced water flow, the problem can often be resolved with a few simple checks.

In our experience, the impeller is one of the first things that should be checked. Debris, sand, grit, plant material or other material entering the filter can restrict or damage the impeller and significantly reduce the performance of the filter.

1. Check & Clean the Impeller First

Always unplug the filter from the power supply before opening or servicing it.

The impeller needs to be completely removed from the impeller housing for proper inspection. Simply looking at the impeller while it is still installed is not sufficient.

Remove and inspect:

The complete impeller
Impeller shaft
Rubber end caps/bushes where fitted
Impeller chamber/housing

Thoroughly clean the impeller chamber and remove any debris, slime, sand, grit or other material.

Carefully inspect the impeller and shaft for:

Cracks or broken components
Bent or damaged shaft
Excessive wear
Missing or damaged rubber end caps
Debris wrapped around the impeller
Build-up inside the impeller chamber

Once cleaned, the impeller should rotate freely on the shaft.

A damaged impeller or shaft may cause the filter to stop, intermittently start, make excessive noise or produce greatly reduced flow.

2. Check the Filter Media

Check that the correct filter media and sponges are being used and that they are installed in the correct positions.

We recommend using genuine Aqua One replacement media designed for your particular Nautilus or Ocellaris model.

Be particularly careful when using aftermarket filter pads, loose filter wool or polyester batting. Material that is too thick, too fine, incorrectly sized or tightly packed can significantly restrict water flow through the canister.

Restricted flow places unnecessary load on the filter and can result in poor performance.

If troubleshooting a low-flow problem, remove any questionable aftermarket media and test the filter using the correct genuine media configuration.

Important: Genuine Aqua One wool pads supplied or specified for your particular filter are suitable for use. The warning above relates particularly to loose or incorrectly sized aftermarket filtration material.

3. Clean the Hoses, Intake & Outlet

Reduced flow is not always caused by the motor.

Check the complete water path, including:

Intake strainer
Intake pipe
Outlet pipe
Spray bar or duckbill outlet
Inlet and outlet hoses
Tap/quick-release assembly

Slime and debris can gradually accumulate inside hoses and pipework and considerably reduce the filter's flow rate.

Remove and thoroughly clean the hoses and pipework using an appropriate aquarium hose/pipe brush.

Also check that none of the hoses are kinked, crushed or bent behind the aquarium or cabinet.

4. Check for an Airlock

Air trapped inside a canister filter can cause:

Reduced or intermittent flow
Rattling or unusual noises
Air bubbles coming from the outlet
Difficulty restarting after maintenance

After restarting the filter, allow several minutes for trapped air to clear.

If necessary, gently rock the canister from side to side/back and forth while it is operating to help trapped air escape.

Check that all hose connections are secure, as a small air leak on the intake side may continually introduce air into the filter.

Also ensure that an air stone or other strong source of bubbles is not positioned close to the filter intake, as these bubbles can be drawn into the canister.

5. Restart the Filter Correctly After Maintenance

Incorrect restarting after cleaning is a common cause of a filter appearing to have failed.

After maintenance:

Make sure the media baskets are correctly seated and aligned.
Check the main O-ring is clean, correctly positioned and undamaged.
Refit and secure the pump head correctly.
Reconnect the inlet and outlet hoses correctly — IN to IN and OUT to OUT.
Make sure the quick-release/tap assembly is fully inserted and locked.
Ensure the intake strainer is completely submerged.
Follow the priming/start-up procedure specified for your particular Nautilus or Ocellaris model.
Once running, allow several minutes for remaining air to leave the system.
Gently rock the canister if necessary to release trapped air.

Do not repeatedly run the filter dry while attempting to get it started.

6. Filter Will Not Prime

If the filter will not prime, check:

Hoses are not kinked
Intake strainer is not blocked
Intake pipe is correctly assembled
IN and OUT hoses have not been reversed
Quick-release/tap connector is fully inserted and locked
Aquarium water level is high enough
All hose connections are secure
There are no obvious air leaks

Follow the correct priming procedure for your particular filter model before assuming the motor has failed.

7. Filter Is Running But Flow Is Very Slow

Work through the following in order:

Completely remove, clean and inspect the impeller and shaft.
Clean the impeller chamber.
Check the intake strainer for blockage.
Clean the intake and outlet pipes.
Clean the complete length of both hoses.
Check hoses for kinks.
Clean or replace clogged filter pads and sponges.
Remove excessively dense or incorrectly fitted aftermarket media.
Confirm the media baskets are correctly assembled.
Check for trapped air inside the canister.

Remember that the advertised maximum flow rate of a canister filter is not necessarily the flow you will see once the filter is installed. Filter media, hose length, vertical head height and normal accumulation of debris will all reduce actual flow.

8. Filter Is Making a Rattling or Grinding Noise

A noisy filter commonly indicates air in the system, a dirty impeller or an impeller/shaft problem.

Turn the filter off and completely remove the impeller.

Check for:

Sand or grit
Snail shells or other debris
Slime build-up
Damaged impeller
Damaged or worn shaft
Damaged/missing rubber end caps
Restricted inlet or outlet flow

After cleaning and reassembling the filter, remove any trapped air by gently rocking the canister.

9. Filter Is Leaking

Immediately disconnect the filter from power and check:

Main pump-head O-ring is installed correctly
O-ring is clean and undamaged
Media baskets are correctly aligned
Pump head is correctly seated
Quick-release/tap connector is fully inserted and locked
Hose connections are secure

The main O-ring can be lightly lubricated with an aquarium-safe lubricant where recommended. Never use petroleum-based lubricants.

Before Contacting Us About a Fault

If your Aqua One Nautilus or Ocellaris filter is still not operating correctly, please complete the following first:

Completely remove and clean the impeller
Inspect the impeller and shaft for damage
Clean the impeller chamber
Clean the intake and outlet pipework
Check and clean the hoses
Check the filter media for excessive restriction
Remove unsuitable aftermarket filter wool/media
Check for trapped air
Restart the filter using the correct priming procedure

If the problem remains after completing these checks, please contact us with your exact filter model and a description of the problem.

Photos or a short video showing the filter in position on the tank, media configuration, impeller and the problem occurring can also make troubleshooting considerably easier and will all be needed for us to make a claim on your behalf with manufacturers