Have Questions About Freshwater External Filters?
We have answers. Get quick help for common questions.
Why should I choose an external filter for my freshwater aquarium?
External filters are ideal for freshwater aquariums because they provide superior filtration compared to internal or hang-on-back filters. They are especially useful for larger tanks or heavily stocked aquariums. They allow for customizable setups, minimize visible equipment inside the tank, and offer more filtration volume, making them effective at maintaining stable water conditions over time.
Are external filters noisy?
Most modern external filters are designed for quiet operation. Brands like Eheim, Oase, and Fluval are especially known for their low-noise motors and smooth performance. Ensuring the filter is properly installed on a flat, cushioned surface also helps minimise any residual vibration or hum.
Can I use an external filter in a planted aquarium?
External filters are an excellent choice for planted aquariums. They provide consistent flow and excellent water clarity without disturbing the aquascape. Many aquascapers prefer external filters because they keep equipment out of view and can be paired with inline heaters or CO₂ diffusers for a sleek, professional look. Some models, like the Oase BioMaster Thermo series, even include a built-in heater to reduce visible hardware in the tank.
How do I prime an external filter?
Priming fills the filter with water before the motor is turned on. Some models, such as the Eheim Classic, require manual filling or siphoning to start the flow. Others, like the Fluval 07 series and Oase FiltoSmart, have a self-priming button that draws water automatically. High-end filters like the Oase BioMaster make priming even easier with quick-start valves and ergonomic design.
Are spare parts and accessories available?
Yes, Charterhouse Aquatics stocks a wide selection of spare parts for all major brands. This includes hoses, connectors, impellers, filter media refills, pre-filters, O-rings, and seals. Accessories like inline heaters, cleaning brushes, and replacement baskets are also available, making it easy to maintain your filter long-term or adapt it to your evolving aquarium needs.
How do I choose the right external filter for my aquarium size?
To choose the right filter, you should match the filter’s capacity to your aquarium volume and select one with a slightly higher flow rate than required. For example, smaller tanks up to 100 litres may be suited to models like the Oase FiltoSmart 100 or Fluval 107. Medium-sized aquariums between 100 and 250 litres work well with filters such as the Eheim Classic 250 or Fluval 207. For larger tanks, models like the Fluval FX4 or Oase BioMaster Thermo 600 provide more power and filtration capacity.
How often should I clean my external filter?
Cleaning frequency depends on the size of your tank, the number of fish, and the amount of waste produced. In general, external filters should be cleaned every four to eight weeks. Mechanical media such as sponges can be gently rinsed in tank water during a water change, while biological media should be disturbed as little as possible to preserve beneficial bacteria. Replace fine polishing pads as needed, and always monitor flow rate to gauge when cleaning is due.
What filter media is best to use?
The best media setup depends on your aquarium’s needs. Most external filters come with a combination of mechanical sponges and biological media such as ceramic rings or sintered glass. You can also include chemical media like activated carbon or phosphate removers to target specific water issues. For planted tanks, it’s often recommended to skip carbon unless removing medications or tannins, as it may also remove nutrients.
What’s the difference between Oase, Fluval, and Eheim filters?
Eheim filters are widely respected for their reliability, simple design, and quiet performance, making them a top choice for hobbyists who value long-term durability. Fluval filters offer great all-round performance, with energy-efficient motors, easy-start systems, and high flow rates across a range of models. Oase filters are more premium and stand out with built-in features like integrated heaters, pre-filter modules, and tool-free maintenance, making them perfect for users who want convenience and flexibility.
Can I use these filters on a marine tank?
While most of the external filters in this collection are designed for freshwater use, some can be adapted for use in fish-only marine systems. However, reef tanks and marine setups with corals typically benefit from sump systems with protein skimmers. Always check the manufacturer’s specifications to ensure compatibility with saltwater conditions.
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.
