Fluidized Bed Filters

Filtering Your Aquarium Water

What Is It?

A fluidized bed filter is a tube that hangs off the back of the tank and is connected to a water pump in the tank. These filters force water through a churning mass of small heavy granules - usually sand, silica chips, or plastic - in the bottom of the tube.

How Does It Work?

Fluidized Bed Filter Diagram Fluidized bed filters provide biological filtration very similar to that provided by under gravel filters. Nitrifying bacteria colonies grow on the surface of the particles of sand in the bed, and process ammonia and Nitrite into Nitrate as the water passes through the sand. Water needs to be pumped into the filter from an external water pump, usually a power head located in the tank. The water is pumped up from the bottom of the filter, through the media, and then flows back into the tank from the top of the filter. Because of the speed at which water is passed through the filter media, it becomes 'fluidized' - the sand is constantly being pushed up by the current and then falling back through the water in response to gravity, similar to the 'snow' in snow globes.

What Maintenance Does It Require?

Fluidized bed filters require very little maintenance. The pump will require regular maintenance, including cleaning the impeller, impeller shaft, and intake and outlet as debris collects and algae and bacteria grow in it causing reduced water flow. You will also need to monitor the sand bed, as it can eventually settle and become stagnant. This should not happen for a long time, maybe even years.

What Should I Be Aware Of?

Fluidized bed filters can be expensive, and they will need to have space behind the tank to hang, so the tank cannot sit flush against a wall. You will also need to monitor the sand bed to make sure that it is still free moving. Fluidized bed filters also may not restart correctly after a power outage.
Fluidized bed filters provide biological filtration.

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