Review - Fluval 304 External Canister Filter

Hagen introduced the new Fluval 104-404 canister filter range to replace the older 103-403 range. The 304 is rated for tanks up to 300 litres. Fluval 304, media compartments

The canister has a separate pre-screen section consisting of 4 rectangular sponges for mechanical filtration, this can be removed separately from the main media compartments. There are 3 main compartments for media, each divided into two halves, for maximum flexibility in media combinations. Carbon pouches and hollow tube bio-media are included. The overall construction seems sturdy and the filter is quiet in use. However, the output is not quite as strong as one might expect from a filter of this size.

Advantages over the older range:

New locking casing clips, which are unlikely to break as the old ones were prone to doing.
Stop system on tubing taps, which shuts off flow when removed from filter.
The rubber sealing ring remains in place when the pump head is removed from the main canister.
Four separate sponges act as a mechanical screen before main media chambers.
Self-priming device.

These filters are also excellent value for money at current UK prices, especially compared to one of their main competitors - the Eheim range. Of course, their long term reliabilty in comparison to the high quality Eheim range is yet to be established.

Update: (Oct 2001)
In longer term use, a couple of problems have become apparent with the filter I have. Firstly, the 'Aquastop' system, which replaces the need for separate taps and should shut off the flow, doesn't work properly, and didn't from quite early on. It tends to become easily clogged with debris which stops the valves working properly. This means that the inlet pipe has to be taken out of the water to prevent the water from continuing to flow. Secondly, I have had trouble with the impellor stopping. On the first occasion, the impellor housing was ready for a clean, so this may have contributed to it. However, because the motor remained on, the housing got very hot, and this melted the plastic part of the impellor fitting. This may have contributed to the filter stopping a second time, after which it would not re-start. As an emergency measure, I had to use a powerhead on the intake pipe to run the (unplugged) filter. The replacement impellor assembly which I bought did not fit the housing (!) - I am unsure whether this is due to wide manufacturing tolerances, or distortion of the impellor housing.
In feedback I have received by email, some have suggested that the flow through these canisters may not pass through the media fully. In one case, cling film had been placed over the top media basket, blocking the normal water path. There was apparently hardly any reduction in flow rate. While this might indicate that the water is able to flow through the canister without passing through the media, I do not feel that this is a completely 'fair' test, because water will always take the path of least resistance, and if the normal route is blocked, the water flow will find an alternative route. This may even be an in-built safety feature by the manufacturers, so that if the media is very clogged with debris, the water can still flow, hence preventing damage to the filter. However, this would make it difficult to judge when the canister required cleaning, and definately suggests the possibility that the water may begin to bypass the media as it naturally becomes clogged.

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Hagen introduced the new Fluval 104-404 canister filter range to replace the older 103-403 range. The 304 is rated for tanks up to 300 litres.
The canister has a separate pre-screen section consisting of 4 rectangular sponges for mechanical filtration, this can be removed separately from the main media compartments. There are 3 main compartments for media, each divided into two halves, for maximum flexibility in media combinations. Carbon pouches and hollow tube bio-media are included. The overall construction seems sturdy and the filter is quiet in use. However, the output is not quite as strong as one might expect from a filter of this size.
Advantages over the older range: New locking casing clips, which are unlikely to break as the old ones were prone to doing. Stop system on tubing taps, which shuts off flow when removed from filter. The rubber sealing ring remains in place when the pump head is removed from the main canister. Four separate sponges act as a mechanical screen before main media chambers. Self-priming device.
These filters are also excellent value for money at current UK prices, especially compared to one of their main competitors - the Eheim range. Of course, their long term reliabilty in comparison to the high quality Eheim range is yet to be established.
Update: (Oct 2001) In longer term use, a couple of problems have become apparent with the filter I have. Firstly, the 'Aquastop' system, which replaces the need for separate taps and should shut off the flow, doesn't work properly, and didn't from quite early on. It tends to become easily clogged with debris which stops the valves working properly. This means that the inlet pipe has to be taken out of the water to prevent the water from continuing to flow. Secondly, I have had trouble with the impellor stopping. On the first occasion, the impellor housing was ready for a clean, so this may have contributed to it. However, because the motor remained on, the housing got very hot, and this melted the plastic part of the impellor fitting. This may have contributed to the filter stopping a second time, after which it would not re-start. As an emergency measure, I had to use a powerhead on the intake pipe to run the (unplugged) filter. The replacement impellor assembly which I bought did not fit the housing (!) - I am unsure whether this is due to wide manufacturing tolerances, or distortion of the impellor housing. In feedback I have received by email, some have suggested that the flow through these canisters may not pass through the media fully. In one case, cling film had been placed over the top media basket, blocking the normal water path. There was apparently hardly any reduction in flow rate. While this might indicate that the water is able to flow through the canister without passing through the media, I do not feel that this is a completely 'fair' test, because water will always take the path of least resistance, and if the normal route is blocked, the water flow will find an alternative route. This may even be an in-built safety feature by the manufacturers, so that if the media is very clogged with debris, the water can still flow, hence preventing damage to the filter. However, this would make it difficult to judge when the canister required cleaning, and definately suggests the possibility that the water may begin to bypass the media as it naturally becomes clogged.