Fluval U1 Underwater Filter Review

The Fluval U1 internal filter is one of the more recent products to hit the market. The advertising claims that it is a strong filter that operates in a quiet manner. According to the specifications, it has a flow rate of 250 litres per hour and may be used in containers that are up to 55 litres.

One of them has been put through its paces in a test environment consisting of just two fish and a few plants in a rather modest tank. The tank has been around for quite some time.

First impressions

Looks ok. It has a robust enough feel to it. The sucker pads find their locations accurately (on of my biggest hates is the cheap suckers on small equipment as they never stay put).
Extremely simple to put together.

First use

It makes quite an impact right from the bat. It caused a significant amount of water movement, and I was afraid that it would cause the tank to get quite agitated; but, after I adjusted it to the appropriate level, it worked well. There was some trial and error involved, but overall, it wasn’t too difficult to figure out how to adjust the flow rate and the air rate. Adjusting the depth at which one is submerged in order to get the desired air flow was one tip that I did discover.

After one month

Irritations. Even if it is still very quiet, it gradually loses its power. It is quite easy for the filter to get blocked. Because it must be cleaned so often, the filter requires that I always have a large supply of water on hand. The promised flip top cannot be used since it prevents the filter from being exposed. Before you can access the foam on the interior of the filter, you will need to remove the whole filter and take it apart completely each time.
The water level drops as a result of evaporation, which also causes a change in the air rate, which means that it must be readjusted once every few days.


It is a wonderful inexpensive filter that is rather compact. It is as silent as a mouse. It serves its purpose well. However, a significant amount of upkeep is required.
Much if it’s a fantastic price, I think you might get something even better elsewhere.

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