Fish tank and aquarium filters

Seasoned fish owners know that the key to happy fish is keeping their aquarium or tank water well filtered. Keeping your fish healthy hinges massively on whether you've got a good filtration system fitted.

The water in a fish tank can quickly become polluted with harmful compounds. Filtration systems are designed to deal with them efficiently, protecting the quality of the water and the health of your fish in the process.

The type of filter you use will depend on the size of your tank, the number of fish you are keeping and the style you personally prefer.

Corner filter

Ideal for smaller fish tanks, the corner filter is usually a small box with holes in the top, sides and bottom. It contains internal layers that use activated charcoal and filtration material to create a mechanical filter. The water is sucked up through the bottom of the filter and expelled from the top once it's been dealt with.

This option is usually the cheapest, but should only be considered for smaller tanks.

Undergravel filter

Undergravel filters are small, slatted plastic trays that lie on the base of your tank, covered with a layer of gravel. They provide a biological filtration system but are usually not as effective on their own.

Most experts would probably advise using an additional filtration system as well as the undergravel filter to ensure that the water is kept as clean as possible. Again, this option should only be considered for small tanks.

Hanging filter

This tends to be the most popular option as it can be applied to many different sizes of tank. These plastic boxes hang on the side of the tank, usually towards the back. Water is sucked into the filter through a long tube that sits in the tank.

Within the box, various chemicals and filtering systems are used to clean the water before it's sent back down into the tank. Hanging filters are extremely easy to clean as the filters can usually be removed without disrupting the environment in the tank.

Canister filter

Another external option, the canister filter has three layers of filtration. As with the hanging filter, the water is sucked out of the tank through a tube and run through the canister to be thoroughly cleaned.

Canister filters tend to be a pretty expensive option - but most would agree they're worth the investment. And as with the hanging filter, they're extremely easy to clean and maintain.


As mentioned, corner filters tend to be the most affordable option. You can pick one up for less than £10. But these filters are only advised for use within very small tanks.

An undergravel filter can also be picked up for around £10 so when used with a corner filter system, they're a very cost-effective option for smaller tanks.

Hanging filters are a little more expensive, usually costing around £15-20 and canister filters can start from £20 and go up to around £150.