Best Aquarium Filters for Sale-Buying Guide

What are aquarium filters?

If you are starting out in aquatics, you may be wondering how important aquarium filters are, and what they are and how necessary they really are. I will tell you that filters are mechanisms that have the mission of filtering the water of the aquarium, to remove impurities that may contain. They take the water of the aquarium and they make it pass through a series of filtering materials, and once biologically purified, they introduce it again in the aquarium. The most important part of the filters is the pump, which sucks the water from the aquarium, forces it through the filters and returns it to the aquarium.

Depending on their position, the aquarium filters are divided into two large groups, external and internal:

  • The external filters are placed outside the aquarium. They are suitable for large aquariums.
  • Internal aquarium filters are placed inside the aquarium. They are usually fitted to small aquariums.

Why are filters so important for the aquarium?

Stagnant water deteriorates if it is not filtered and oxygenated. In addition to the deterioration of the water itself, we must add the deterioration caused by the fish in the water, which leave behind food and their own physiological waste. In a natural environment, the physiological remains and food produced by fish decompose and end up being processed by nature without any problem. But in an aquarium this does not happen. The amount of organic waste far exceeds the limits that the aquarium can process biologically. In the end, the decomposition process generates toxic elements for the fish. We must provide the aquarium with a filtration system so that the water quality is ensured and the life of the fish is not endangered.

Aquarium filter types

It may seem that there is a huge number of filters for fish tanks or aquariums, and it is true, because each manufacturer offers a wide range of filters, with the intention of covering all the needs that users pose to them.

There are basically two types of filters, external and internal. I think it is clear that the internal filters are inside the aquarium, while the external filters are outside the aquarium.

So, depending on where the filter is installed and its own characteristics, we have the following types of filters:

Internal aquarium filter

The internal filters, as their name suggests, are placed inside the aquarium. Today there are very efficient internal filters, just as any other filter type.
Their position inside the aquarium offers advantages and disadvantages.

Advantages of internal aquarium filters

  • Silent. The aquarium itself dampens any noise they may produce.
  • They are very easy to use.
  • They are basically designed for small aquariums, which are many of those sold.
  • They are very, very cheap.

Disadvantages of indoor aquarium filters

  • They occupy space inside the aquarium, which could be occupied by fish, decoration, plants…
  • If we don’t manage to hide them well, they are quite unsightly.
  • They require more maintenance than other filter models.

Backpack filter or waterfall filter

It is curious, they are called waterfall filters because, when filtering, the water returns to the aquarium “falling” as if it were a waterfall. And backpack, because they are placed on the side or back of the aquarium, as if they had hung a backpack.
As with internal aquarium filters, they have their advantages and disadvantages:

Advantages of backpack filters

  • They do not take up space inside the aquarium
  • They have a great filtration power, you have waterfall filters for aquariums of 300 liters or more
  • Different filter media configurations are supported
  • They are very easy to handle, and require less maintenance

Disadvantages of cascade filters

  • Higher noise level than internal filters
  • Limitation (same as interns) on the size of the aquarium
  • If you can’t hide them, they’re still pretty unsightly

External aquarium filters

External filters are placed outside the aquarium and can remain completely hidden, usually under the aquarium.
They have many advantages over other filters and are often used in large aquariums, but gradually, because of the great advantages they offer, more hobbyists are using them.
They are composed by a series of rubbers, that extract and return the water to the aquarium, connected to a glass where the filter materials are.

Advantages of external aquarium filters

  • Higher filtration capacity than any of the other options
  • Fully customized filter media configuration
  • Maintenance and cleaning tasks are greatly reduced
  • Hardly any noise, because they are also hidden in furniture
  • We win in aesthetics, they are not in sight

Disadvantages of outdoor aquarium filters

  • Usually, but not always, they are somewhat more expensive
  • We need to enable a place to hide them

Filter systems, filter types

Although from the beginning I am talking about the aquarium filters as if they were the only element that influences the quality of the water, in reality this is not the case.
Aquarium filters are part of what would be a filter system.
A filter system consists of the filter and all those elements that help the nitrogen cycle to take place.
In that sense the types of filtering can be

  • Biological
  • Mechanics
  • Chemicals

Biological filtering

The most important (indispensable) part of the water quality is the biological filtering of the aquarium. We achieve a biological filtering of the aquarium, promoting the emergence of bacteria involved in the process of nitrification of water.

The bacteria settle on porous materials, such as sponges in “mechanical” filters, but are also present in the aquarium substrate, sand, gravel or stones in the aquarium. They can be promoted by adding porous materials, such as ceramic balls and cuvettes, to the aquarium.

Mechanical filtration

The mechanical filtering cleans the solid particles that are kept in suspension in the water, preventing them from reaching the bottom of the aquarium, where they would already depend on the biological filtering to deteriorate.

It has its limitations, as the debris that is absorbed by the filter will continue its decomposition process within the filter. It may even be the case that the smaller particles are not completely removed and return to the aquarium.

Mechanical filters have a number of elements that must be cleaned regularly, even some of the filter materials must be replaced periodically, because they can not be cleaned. In order for the filter to fulfil its task as well as possible, it is ideal to place a filter element with larger pores (sponge), which retains the larger elements, and behind it one with finer pores, for the smaller particles.

Mechanical filter maintenance
Keeping the filters in perfect condition ensures that the quality of the water is optimal.

  • The maintenance of the filters has to be periodic, but it becomes indispensable if we observe that the flow of the water that the pump pours to the aquarium has diminished.
  • The filter sponge contains most of the bacteria responsible for nitrification. We can clean it without any problems, but we will only do it in depth, if it is clear that there are other bacteria colonies.
  • If we remove all the bacteria, we will have a big problem with cycling.
  • We should never use tap water, which contains chlorine and is lethal to bacteria. The ideal is to use clean water from the aquarium itself.
  • Some filter materials can not be cleaned, once the filter is saturated you have to discard it and put a new one.

Aquarium chemical filtration

The chemical filtration of the aquarium is carried out as something exceptional, when we have some concrete problem with the quality of the water, which we must solve immediately.

A common trick is to use activated carbon to collect the remains of medication, when they are no longer needed.
What we are looking for with chemical filtration is:

  • Modify the hardness of the water
  • Change the pH of the water
  • Eliminate chlorine
  • Neutralize the appearance of heavy metals
  • Eliminate bad odors that may be produced by water
  • Correcting water coloring
  • They are also useful for trapping toxins

The chemical filters must be placed behind the mechanical filters, i.e. behind the sponges. The most common are activated carbon, peat and absorbent resins. Once they have fulfilled their function, they must be completely removed. They are not cleaned, nor do they serve for other times.

How to choose an aquarium filter?

There are a large number of filters on the market, designed for all types of aquariums and fish tanks.
There are many ways to find out which filter best suits your needs, but you can rule out filters by using the following questions:

How big is my aquarium or fish tank? Flow rate litres/hour

The capacity of the filter to do its job is measured in liters/hour.
The filter you choose must be capable of moving 3 times the liters of your aquarium in one hour.
For example, if you have a 40 liter aquarium, the filter should have a flow rate of 120 litres/hour.

Where will I put my aquarium?

The best-selling filters are internal aquarium filters. These filters are placed inside the aquarium, with the consequent loss of useful space.
However, they are the perfect solution if the space for our aquarium is limited, or if it goes in a very visible place where it would be unsightly to place a backpack filter or an external filter.
As you can see, knowing where we will place our aquarium, as well as calculating the space we have available, will help us make the decision on which filter to use.

What is the best aquarium filter on the market?

Internal aquarium filters, with bubblesAquarium filters are necessary to maintain the quality of the water inside the aquarium, and as a consequence, that life inside the aquarium is possible.

They not only help to keep the water clean by removing impurities, they are vital for maintaining bacteria colonies, which in turn are essential for maintaining the right water parameters.

An aquarium without a filter is a death trap for fish and plants. That is why it is so important to choose well, among the different options available, and to help you in that choice, I have prepared a comparison of what are probably the best aquarium filters at this time.