The mission of the freshwater aquarium filter

The aquarium being a closed environment, the water does not circulate naturally, which prevents it from regenerating and oxygenating. Other health risks to your fish are mainly waste buildup and acidity defects.

Filtering consists of aerating the water, as well as removing insoluble particles and nitrogenous toxic elements generated by fish and plants. Thus, the water is kept stable, favorable to the good health of the fish.

The three factors for choosing the flow rate of your freshwater aquarium filter

The choice of your freshwater aquarium filter is made on aesthetic factors, but above all by considering the flow rate of the filter, corresponding to the volume that can be purified per hour.

The required flow depends on three criteria: the fauna and flora of your aquarium, the volume of the aquarium and the volume of the filter itself.

The fauna and flora of your aquarium

The flow rate of the filter you need depends on the species that live there, as well as the number of animals in relation to the volume. You should also consider the species you select.

There is a wide variety of freshwater fish. Not everyone has the same needs and does not "pollute" your water in the same way. Some are also more restless than others, which influences the turbidity of the water if they move the waste, but also the oxygenation of the water.

On the other hand, you should be interested in the nature of the flora that grows in your aquarium. All plants do not have the same needs and the same consumption.

The volume of the aquarium

All filters specify the volume of water for which they are designed. The volume you select should always be above reality: it can triple the expected throughput, and even go beyond, up to multiplying it by ten. If, for example, your aquarium contains 100 liters of water, your filter must be able to treat 300 liters of water per hour.

In any case, never select a filter whose power is less than or equal to the volume of fresh water in your aquarium, because you expose your fish to great danger.

Filter volume

The last criteria you need to check is the volume of the filter itself. Its flow corresponds to the volume of water treated and depends on the power of its pump, but you must also take into account the quality of the filtration. This is influenced by the volume of the filter and the characteristics of its filter media. A larger filter will prove more efficient and require less maintenance.

If you choose an internal filter, which is by nature smaller, select a flow rate at least three times greater than the volume of your aquarium to be more serene. However, you will need to clean the filter media more regularly than with a larger filter whenever you notice that the flow rate of the treated water is dropping.

The different filters for a freshwater aquarium

There are different types of filters: internal, external, cascading, enhancer or natural. Each has its characteristics, advantages and disadvantages. On the other hand, your choice is not completely free, since not all of them are able to deal with large aquariums.

The internal filter for freshwater aquariums

The most popular filter is the internal filter which, as its name suggests, is placed inside the aquarium. A space is reserved for the settling tank and the pump which generates eddies to direct the water through the filtration system.

The advantage of this type of filter is to be economical, compact, rather silent and reliable. The filter is placed inside, you do not risk leaks.

On the other hand, the internal filter reduces the living space of your fish. Moreover, it is not always possible to move it and you can deplore its unsightly appearance. You can get around this drawback by hiding it in the layout of your aquarium, behind plants or decorations.  

The volume of the internal filter is limited, which requires you to clean it regularly. The intervals fluctuate from 2 weeks to 2 months, depending on the volume of your aquarium, as well as the fauna and flora it houses. Take care not to let waste escape into the aquarium when performing the manipulation.

Despite everything, the internal filter remains the most practical. It is ideal for aquariums up to 150 to 200 liters.

The external filter

The external filter – therefore placed outside the aquarium – is more suitable for large volume aquariums. The external filter has a larger filtration volume, which makes it all the more efficient. It's up to you to find how to hide it in the cabinet that houses the tank or under the aquarium.

The external filter draws in water which passes through a strainer, a perforated part which acts as a filter at the entrance to a pipe and prevents fish from being sucked in. It filters the water, then discharges it away from the tank, in order to create a permanent flow of water.

Much more powerful than the internal filter, the external filter has the advantage of not cluttering up the living space of your fish, while providing them with healthy water, including for very large aquariums. It also requires less maintenance, thanks in particular to its large volume. On the other hand, maintenance is a little more complicated.

Pay attention to the assembly of the external filter

Before installing a large capacity aquarium (over 200 litres) which requires an external filter, plan the location of the external filter. In addition, your assembly must be exemplary so as not to risk water leaks outside your tank. After each interview, make sure you have repositioned the device properly to avoid any unpleasant surprises.

The external filter is an essential solution for a large aquarium, especially if you place rather polluting fish there. Take an interest in its noise level before buying it, because a nagging hum can quickly become annoying, but don't worry, most filters these days are very quiet.

The waterfall filter

The cascade filter is also an external filter, but reserved for smaller volumes, not exceeding 50 to 100 liters. For a higher volume, you can find a cascade filter equipped with a double compartment to optimize filtration.

Also called a hanging filter, it is only compatible with open aquariums, as it rests on their rim.

The waterfall filter does not have a large flow, it is chosen more for its aesthetics. However, it will be suitable if your tank is sparsely populated or your fish are not major polluters.

 The waterfall filter has many advantages:

• compact
• easy to install
• easy to maintain
• economic.

The enhancer filter

The enhancer filter – or sponge filter – is a more rudimentary filter. It consists of a plastic tube open at the top, and surrounded by a sponge at the bottom. Its air pump works mechanically.

The exhaust filter is particularly suitable for aquariums with invertebrates and very small fish. As the suction is distributed over the entire surface of the foam, the animals are not at risk of being sucked in. The flow created turns out to be smoother than with the other filters.

The enhancer filter is often criticized for an unattractive aesthetic. However, you can camouflage it behind decorations or vegetation. It can also be a bit noisy, due to bubbles bursting on the surface. It suffices in this case to move the top of the tube to the surface to attenuate the sounds.

The exhaust filter is not suitable if you need a high flow rate and your fish are rather polluting. It must in any case be reserved for small aquariums, not exceeding 50 liters.

However, it has multiple advantages. It is the most economical of the filters and its installation is very simple. Finally, its maintenance is as rudimentary as its design.

The aquaponics filter

The aquaponics filter or natural filter is composed of natural elements, therefore more ecological. It remains reserved for aquariums whose volume remains less than 40 liters.

Aquaponics means cultivation of plants associated with the breeding of fish, whose droppings are used in particular as fertilizer. You therefore need to grow green plants that feed on the nitrates produced by the fish.

The aquaponics filter is the most aesthetic of all, thanks to its natural appearance. Placed in a coconut shell filled with clay balls, it works with plants to clean the water in the tank. You can thus create very attractive decorations which extend outside your aquarium.

The aquaponics filter does not clutter the aquarium, as it fits perfectly into it. Ecological and responsible, it saves you from having to change the water.