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External Aquarium Filters

External canister filters are ideal for large aquariums and for coping with large tropical fish or goldfish. External filters are able to hold large amounts of filter media and provide excellent biological and mechanical filtration. Charterhouse Aquatics stock all the biggest brands of external filter and external filter media for you to buy including Eheim, Oase, Tetra, Fluval and many many more.
 Have questions about External Aquarium Filters? Checkout our FAQ!

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Have Questions About External Aquarium Filters?

We have answers. Get quick help for common questions.

1. What size external filter do I need?
Choose a filter rated for at least your tank's volume, and go larger for big or messy fish such as cichlids and goldfish.
3. How often should I clean an external filter?
Usually every 4 to 8 weeks. Rinse the sponges in old tank water, never tap water, so you keep the beneficial bacteria.
5. How do I start a new external filter?
Fill the canister with water, prime it (many models have a built-in primer), then switch on and check every hose connection for leaks.
2. Are external filters better than internal filters?
They hold far more media, so they give stronger biological filtration and need cleaning less often. They also free up space inside the tank.
4. Where does an external filter go?
Usually in the cabinet below the tank, with the intake and return pipes running over the back. Keeping it below the tank helps it prime and run correctly.
6. What media should go in an external filter?
Most use layers: sponge to trap debris, biological media such as ceramic rings to house bacteria, and fine floss to polish the water. Follow the order your filter's manual gives.

Shop External Aquarium Filters for Crystal-Clear Water

Keep your aquarium water clean, healthy, and stable with our range of high-performance external filters. At Charterhouse Aquatics, we stock a wide selection of trusted brands including Eheim, Oase, Fluval, and Tetra—ideal for freshwater, planted, and tropical aquariums of all sizes. External canister filters are a popular choice among hobbyists for their superior mechanical and biological filtration, quiet operation, and ease of maintenance. Whether you’re running a compact nano tank or a heavily stocked community setup, we have the right solution to suit your needs. From beginner-friendly filter kits to advanced models with electronic control and adjustable flow, our range covers every level of experience and tank type. Not sure which filter is right for your aquarium? Our expert team is here to help you find the best match for your tank size, livestock, and filtration goals. We also carry a full selection of replacement media, hoses, impellers, and other essential filter accessories to keep your system running at peak performance. Explore the full collection of external aquarium filters today and enjoy fast UK delivery and top-tier customer support with every order.
Shop External Aquarium Filters for Crystal-Clear Water

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