How to clean an external filter

External filters usually come with either taps, or an auto stop system to stop the water flowing. For this guide I am showing an autolock system filter (fluval 304)

Taps in the on position.


Auto lock system in the on position.



First switch off your filter at the mains, then turn your autolock system to the off position.


Gently lift out the pipework from the powerhead.


Leaving just the main canister, now you can lift off the top section (powerhead)


It is a good idea to place the top section in a bucket or on a towel to catch any remaining water.


Part fill another bucket or container with water from the main tank.


In this water gently wash through all your media, you can change the water for more tank water if it gets too dirty.


Empty the canister part of dirty water.


And re-fill with your rinsed media.


Make sure your outlet (where the water comes into the tank) is above the water line, then open your autolock valve over a bucket of water, this will empty the outlet pipe ready to re-fill the canister. This will also remove loose debris from your pipes.


Top Tip!!! Once you have connected your pipework back to your filter, add an additional pipe to the outlet pipe of your filter and put it into a bucket. Now you can open up your autolock and re-fill the filter. Doing this will help stop any more debris held in the pipework from going into your tank.


Once the filter has filled and pressurised (you will sometimes hear a popping sound) you can turn your filter back on at the mains. Leave the additional pipe in the bucket, this will stop additional debris going into your tank.


Once the water runs clear you can remove the pipe from your outlet pipe on your filter.

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