If you have ever wondered how crystal clear water and the health of its inhabitants are maintained in an aquarium, the answer lies largely in the filtration system. An external filter is a real workhorse that does most of the work to maintain the biological balance in your underwater world.
Unlike internal filters, which take up space inside the aquarium, external filters are separate sealed cylinders or boxes. It is usually hidden in a cabinet under the aquarium, making it completely invisible. This is a big advantage, as it does not disturb the aesthetics of your living landscape.
It works on a simple and effective principle: water from the aquarium is sucked into this external unit through hoses, passes through several compartments with different filter materials, and returns back already purified. Inside, not only is visible dirt removed, but more importantly, beneficial bacteria settle in, neutralizing substances that are harmful to fish.
In essence, it is a self-contained biostation, hidden from view. It does not create unnecessary noise and does not interfere with your observation of the fish, performing its work quietly and reliably. A properly selected external filter is a long-term investment in the stability and beauty of your aquarium.
Device, principle of operation, advantages and disadvantages
External filters are often called canister filters. They are most often placed next to the aquarium. They are placed below the water level, into which two hoses are inserted. One is needed to draw water, and the other to return it to the aquarium. The main purpose of an external filter is to purify water in large, densely populated aquariums.
The filter design consists of several cleaning compartments:
A pump is located at the top of the filters, with a reservoir containing filter materials for chemical, mechanical, and biological purification below it.
External filters need to be cleaned much less frequently than internal ones. This should be done once every 2-3 months.
Compared to internal filters, external filters have a more sophisticated design. They make the water in the aquarium as clean as possible. Water from the aquarium is pumped through the intake hose into the mechanical cleaning compartment, where it undergoes biochemical cleaning and then returns to the aquarium. Depending on the design of the model, the water can flow from top to bottom or vice versa.
Advantages of external filters:
- no noise during operation
- good water purification quality
- combined filtration;
- long service life (more than 8 years);
- can be used for marine and freshwater aquariums.
Disadvantages:
- high cost;
- possibility of leaks;
- large dimensions.
An external aquarium filter is a device that is installed behind the tank and purifies the water by passing it through filter materials. It is needed to remove debris and harmful substances and maintain cleanliness without taking up useful space in the aquarium. It works simply: the pump draws dirty water through a hose, it passes through sponges, charcoal, or other fillers, and clean water returns back. This filter is suitable for medium and large aquariums, operates quietly, and requires infrequent cleaning.
Best external filters for aquariums
The rating is based on popularity among aquarists.
Hydor Professional
Country of manufacture: Italy. This inexpensive but reliable model is available in five filters with different canister volumes. The device provides mechanical and biological water filtration. The fillers (sponge and activated carbon) are located in two special baskets.
The filter is designed for marine and freshwater aquariums. The design is equipped with special gaskets that prevent water from leaking out of the filter during the cleaning process.
Advantages:
- easy start function;
- easy to maintain;
- quiet operation;
- affordable price;
- well-thought-out design.
Eheim eXperience
Country of manufacture: Germany. This model is the basic model in the “professional” generation. It has a square plastic body and is designed for marine and freshwater aquariums. The design is equipped with improved fillers, a pump, and a rotor. The baskets have a full or partial cleaning function. Safe filter operation is ensured by a safety adapter. A prefilter is installed at the water inlet to the design.
Eheim eXperience provides mechanical, biological, and chemical filtration.
Advantages:
- noiseless operation;
- economical energy consumption;
- high filtration quality;
- presence of a prefilter.
Hagen Fluval
Country of manufacture: Italy. The model is designed for marine and freshwater aquariums. It provides high-quality mechanical, biological, and chemical water purification. Despite its high power, Hagen Fluval has low energy consumption. The filter has a convenient start-up mechanism. The design is easy to disassemble and assemble, which facilitates the maintenance process. The filter has 4 types of fillers.
Advantages:
- quiet operation;
- reliable design;
- high performance;
- optimal price-quality ratio.
Disadvantages:
- possible leakage from taps;
- imperfect filler configuration.
Tetra EX
Country of manufacture: Germany. The model is designed for filtering water in aquariums. The design includes 5 filter elements. They are located in special baskets. Tetra EX provides crystal clear water filtration that is safe for fish. The model has valves for adjusting the liquid pressure, as well as a pre-filtration function.
Advantages:
- hose and tube adjustment available;
- reliability.
- high performance.
- fast and high-quality cleaning;
- ease of maintenance.
Aquael Maxi Kani
Country of manufacture: Poland. A new model of canister filters that can work as both external and internal filters in saltwater and freshwater aquariums. It is a device with a remote pump. The standard pump can be replaced with a more powerful one from other manufacturers, suitable for connecting hoses with a diameter of 16/22 mm. Aquael Maxi Kani can be installed above the aquarium.
Advantages:
- well-thought-out design solution;
- high performance;
- no possibility of leaks.
- reliability in operation;
- easy maintenance.
Disadvantages:
- hoses cut into 1.5 m lengths;
- problems may arise when starting a filter installed above the aquarium.
Sera Fil Bioactive
This German brand is manufactured in China. These are multi-purpose filters with a built-in UV sterilizer that irradiates the water after it has been filtered. This helps to destroy pathogens and algae in the aquarium at the reproduction stage. They are designed to filter fresh water only. All filters are equipped with sera zipporax filter material, which is highly effective, and a biological activator.
The filter has a special flute-type nozzle for aerating the water. The device body rests on stable rubber feet.
Advantages:
- low power consumption;
- quiet operation;
- reliable operation and long service life;
- convenient filter start-up;
- easy maintenance.
JBL CristalProfi
Country of manufacture: Germany. The model is designed for mechanical and biological filtration of water in marine and freshwater aquariums. The design is equipped with a quick start button. It is distinguished by its economical energy consumption. It has a pleasant design. The presence of a safety valve in the filter prevents leakage.
Advantages:
- low energy consumption;
- ease of maintenance.
- reliable design;
- high performance.
Disadvantages:
- no protection against clogging with algae pieces;
- frequent filter replacement.
SICCE WHALE
Country of manufacture: Italy. This is a new model that is not yet widely available on the Russian market. The filter housing, made of glossy plastic, has no handles for carrying it. They have been replaced by special holes that are easy to grip.
The set includes a 3 m hose and a bag with accessories for connecting the filter. The hose adapter is recessed into the filter head. The start system is located on the inlet elbow of the hoses. Four baskets with fillers are inserted into the filter housing. Ceramic rings for breaking up the water are located above all the others.
Advantages:
- trouble-free start-up;
- the pump provides good water pressure;
- high-quality assembly;
- high performance.
Disadvantages:
- no sprinkler included;
- noise during operation.
ATMAN DF
Country of manufacture: China. Easy to assemble model. The device has a water pumping function. It starts up quickly and smoothly. Inside the housing, there are three baskets with different fillers. Water aeration occurs during filtration. The outlet and inlet valves are located on the same panel. This is a feature of this series of DF purifiers. They are securely fixed to the filter cover with a special lever.
Advantages:
- high performance;
- quiet operation;
- absolute tightness;
- ease of maintenance;
- reliability in operation.
Eheim Professional 4
Country of manufacture – Germany. The model can be used to purify water in marine and freshwater aquariums. It has a new generation suction adapter that ensures high filter performance. The powerful motor has low power consumption. The pump is located on a ceramic shaft and has a powerful impeller.
This model is characterized by its increased strength and wear resistance. The filter housing is made of durable plastic, and the head is equipped with additional stiffening ribs. The kit includes lubricant for the profiled rubber gasket, which extends its service life. The filter substrate fillers are placed in cartridges.
Advantages:
- low power consumption;
- high performance;
- good filtration quality;
- reliability and quiet operation;
- easy maintenance.
AQUAEL Ultramax
Country of manufacture – Poland. The canister-type model is designed for filtering and aerating water in aquariums. Cleaning is carried out by mechanical, biological, and chemical means. The ceramic rotor shaft ensures quiet operation of the filter.
Advantages:
- quiet operation;
- good water purification and aeration quality;
- economical energy consumption;
- reliability in operation;
- easy maintenance.
Q&A
Is it possible to increase the performance of an external aquarium filter by replacing some of the sponges with ceramic ones?
As a result of such a replacement, the performance will not change radically. Mechanical filtration will deteriorate and biological water purification will improve.
The sponges at the inlet are constantly clogging. How can the filter be improved so that it needs to be disassembled for cleaning less often?
Try putting a mesh on the intake pipe instead of sponges.
What should you pay attention to when buying external filters for an aquarium?
When buying external water purifiers, pay attention to the ratio of the canister and pump sizes. In unsuccessful designs, a large pump is combined with a small canister.
What type of external filters for aquariums are best to purchase with a focus on biochemical filtration?
For this type of cleaning, it is better to purchase external container-type filters. Where mechanical water purification is more important, containerless external filters are installed.
In the end, an external filter is a real workhorse for keeping your aquarium clean and healthy. It works quietly outside, providing powerful and high-quality filtration that most internal models cannot match. Its main advantages are its large volume for filter materials and effective multi-stage water purification.
The principle of its operation is quite simple: water is taken from the aquarium, passes sequentially through mechanical, chemical, and biological fillers in the canister baskets, and then returns purified and saturated with oxygen. This system creates a stable environment for beneficial bacteria, which is critical for biological balance.
Choosing an external filter is an investment in the long-term well-being of your underwater world. It eliminates the need for frequent cleaning inside the aquarium, operates quietly, and does not take up valuable space among decorations and plants. Although its installation and maintenance require a little more effort, the result — crystal clear water and healthy fish — is definitely worth it.
