How Do I Troubleshoot the Impeller For the Fluval 304?

Written by tammie painter Google
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How Do I Troubleshoot the Impeller For the Fluval 304?
The Fluval 304 keeps your tank clean and your fish healthy. (aquarium image by Henryk Olszewski from

The Fluval 304 is an external canister filtration system for home aquariums. The 04 series of Fluval filters features a transparent cover so you can see when the impeller needs maintenance. An impeller is the motorised part of the Fluval 304 that moves the water in the tank over the filter media within the canister. If the impeller becomes clogged with debris, it will not function efficiently. Cleaning and assembling the impeller correctly should solve most problems unless the impeller is broken.

Skill level:

Things you need

  • Retrieval tool (supplied with your Fluval 304)
  • Soft-bristled brush (Optional)

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  1. 1

    Unplug the Fluval 304 from the electrical socket.

  2. 2

    Pinch the two tabs on the impeller cover to open the impeller well. The impeller cover is located on the underside of the lid of the filtration unit. This exposes the impeller fan.

  3. 3

    Pull the impeller fan and impeller from the impeller well.

  4. 4

    Insert the hooked end of the retrieval tool -- also called the ceramic shaft tool -- that came with your Fluval 304 into the hole in the centre of the impeller well. Hook the tool onto the ceramic shaft assembly and pull it out gently. Pull up as straight as possible.

  5. 5

    Rinse all the parts you removed in clean water. If any debris won't come off, use a soft-bristled brush to carefully scrub away any grime.

  6. 6

    Inspect all parts for damage or wear. If any piece appears broken, bent or worn, order new parts through your local Fluval dealer.

  7. 7

    Reassemble the impeller. Reinsert the ceramic shaft assembly into the hole in the centre of the impeller well. Replace the impeller and impeller fan with the shaft of the impeller inserted into the cover's support ring. Place the cover back onto the impeller well and turn it until you hear a "click." Replace the lid onto the canister and plug the filter back into the outlet.

Tips and warnings

  • The cover of the impeller well must be locked into place with the tabs, or the impeller unit won't work properly and could fall out when the lid is replaced.
  • The impeller in the 04 series has a self-cleaning mechanism; but if you are having trouble with any water flow issues, you should assume you have a dirty, broken or worn impeller. Take the impeller apart to clean and inspect it thoroughly.
  • The ceramic shaft is fragile. Avoid applying lateral pressure when cleaning it. If your water flow has decreased, it is most likely due to a broken ceramic shaft.

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