What Are Aquarium Filters Made Of? (Entire Internal Construction)

Image of internals of an aquarium filter

Aquarium filters remove the contaminants in a tank and purify the water, making it a safe, inhabitable place for aquatic animals and plants. But have you ever wondered how aquarium filters accomplish this task? Or, more importantly, what are aquarium filters made of?

Depending on the make and model, aquarium filters are made of mechanical, chemical, or biological components called filter media. Filter media like sponges, gravel, silicon, carbon, and filter wool are placed inside the compartments to perform filtration. Filters also have a shock-proof plastic box.

Let’s now look at the aquarium filter construction in more detail.

Essential Parts Of An Aquarium Filter

Aquarium filters come in different sizes, shapes, and designs.

We can broadly classify them into two main categories: external and internal.

Internal filters are small and compact to fit inside a fish tank.

Water from the tank continuously enters into the filter, where it undergoes filtration and returns into the tank through the outlet pipe.

Internal filters clean and filter small amounts of water.

They are not suitable for large fish tanks with a lot of aquatic pets and plants.

External filters are better suited for large aquariums. They are big and bulky compared to internal filters.

Due to their size, you cannot place them inside an aquarium. They need a special arrangement outside the fish tank.

Water from the aquarium enters into an external filter through an inlet pipe.

It passes through the filter media, which traps the dirt and eliminates dissolved toxins.

By the end of the filtration process, the water is clean and returns to the aquarium through an outlet pipe.

Regardless of whether you have an internal or external filter, aquarium filters use one or more of the three filtration techniques to clean the water.

They are mechanical filtration, chemical filtration, and biological filtration.

To improve efficiency and water hygiene, filters usually use more than one type of filter media.

Hence, the filter media is the single most important component of an aquarium filter.

1. Mechanical Filtration

Fish and other aquatic organisms expel natural waste into their surroundings.

This organic waste contains unsightly particles and toxins.

Apart from the waste that fish eliminate, leftover food, dead or decaying plant parts, and dust pollute aquarium water.

Mechanical filter media removes physical waste from the water and makes it look clean.

It traps solid waste and lets the remaining water return to the tank.

Commonly used mechanical filter media are sponges, wool, fiber, foam, and straw.

Over time, this coarse media traps more and more waste and gets clogged up.

So you need to clean it often to get rid of the trapped solids.

2. Chemical Filtration

Since aquariums are closed systems, they are prone to water chemistry changes.

Even if you use conditioned tap water for your aquatic ecosystem, natural toxins produced by fish will cause the pH and chemical levels to fluctuate.

Unfortunately, aquarium plants and animals are very sensitive to these changes.

When exposed to toxins for a long time, they tend to get stressed and develop health issues.

Chemical filtration helps control this problem.

Commonly used chemical media are poly filters, activated carbon, resins, and other adsorbent media.

These substances react with the heavy metals, toxins, and chemical impurities in the water and neutralize them.

Some chemical filters also use ion exchange resins to remove medications and other contaminants from the water.

Recommended Further Reading:

3. Biological Filtration

Nature has a wonderful, natural mechanism of converting natural toxins like ammonia and nitrites into less harmful substances.

This action is called biological filtration.

Nitrifying bacteria like Nitrosomonas and Nitrobacter perform this task in nature.

Nitrifying bacteria are present everywhere, including aquariums that house fish and other aquatic organisms.

However, they take time to establish a colony and set up a continuous nitrifying cycle in a new aquarium setting.

In an aquarium, aquatic animals like fish eliminate natural waste into the surrounding water.

Over time, this organic waste breaks down and releases harmful substances like ammonia into the water.

When there is no proper filtration system, the ammonia level tends to increase over time.

The fish are continuously exposed to these harmful toxins in their surroundings.

This adversely affects their health and stresses them.

Moreover, sudden ammonia spikes in the water can drastically affect them and can even be fatal.

However, a biological filter can control this issue to a great extent.

Biological media are substances or surfaces on which natural nitrifying bacteria live.

Once you introduce a colony of nitrifying bacteria into the tank through biological filter media, they replicate and grow large enough to handle a self-sustainable nitrogen cycle.

The nitrifying bacteria act on the ammonia and nitrites in the tank and convert them into less harmful nitrates.

By doing so, they maintain a healthy and safe environment for the inhabitants of the tank.

Biological filter media include porous substances like Bio-glass and Matrix.

Helpful bacteria also live on the gravel, substrate, sponges, and other surfaces of the tank.

Once they grow to a suitable size, the aquarium develops an established nitrogen cycle and becomes self-sustaining.

Interesting Further Reading:

How To Make A Biological Filter For Aquariums?

Establishing a self-sustainable and working biological filtration system in a tank is more difficult than setting up a mechanical or chemical filtration system.

Nevertheless, you can start a biological filter with a few essential components and gear up your system for efficient biological filtration with the following steps:

  • You will need non-corroding materials like plastic, rock, ceramic, or fiberglass with enough surface area to hold colonies of nitrifying bacteria.
  • The next step is to introduce nitrifying bacteria into the arrangement. For this, you can use water or filter media from an established tank. This is called the starter material.
  • While starting the biofilter with material from an established tank, take care not to introduce pathogens from the other system into your new tank.
  • Prepare the water chemistry of the tank to support the growth of the nitrifying bacteria. Ensure good water quality for better health and growth rate of the bacteria. Also, adjust the pH, salinity, alkalinity, and water hardness.
  • To speed up the growth of the bacteria, slightly raise the temperature and create a better living condition for the colony.
  • Before introducing the bacteria, add ammonia into the tank. You can use ammonium hydroxide, ammonium chloride, or ammonium nitrite for this. Next, add the nitrifying bacteria into the tank.
  • Measure the ammonia and nitrite concentrations of the tank at regular intervals using a testing kit. Track the readings to identify if the colony is establishing itself.
  • When the Nitrobacter have developed a colony of suitable size, the nitrite concentration of the water will fall. This indicates that the system is stabilizing. So, you should be able to introduce your fish stock into the setting soon.
  • When the nitrite and ammonia levels are acceptable for your fish and aquatic pets, you can introduce them into the tank.

Once you have a consistent nitrogen cycle in your tank, the bacteria will tackle the biological load by themselves.

However, issues can arise when you introduce new fish or wrongly clean the filter media.

If you unknowingly wash away the helpful bacteria colonies from your tank, it will again take time to establish a colony of bacteria and create a sustainable nitrogen cycle.

Remember that chlorine in tap water destroys nitrifying bacteria.

The bio-filter will lose its nitrification capacity if you wash it in plain water.

So, make sure to remove the biological filter components before disinfecting the tank and avoiding exposure to chlorine and other cleaning agents.


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