7 Types Of Fish Tank Filters (Which One Is The Best?)

Image of a fish tank with a filter

Cleanliness is of utmost importance when you keep fish and other aquatic creatures in a closed space like an aquarium. Hence, filters are one of the key components of a good aquarium. A filter makes the tank water safe for the fish by continuously cleaning the water. So, what are the various types of fish tank filters?

The seven types of fish tank filters are sponge, box, canister, fluidized bed, power, trickle, and under gravel. They use mechanical, chemical, and biological filtration methods. Most filters use two of these three methods to remove the free-floating waste and dissolved contaminants from the water.

Let us try to understand how each of these methods works.

Different Types Of Filtration Methods For Fish Tanks

Technically, there are three ways to filter aquarium water. They are mechanical filtration, chemical filtration, and biological filtration. Each method uses different principles and equipment to filter the contaminants from the water.

1. Mechanical Filtration

The basic principle of mechanical filtration is the separation of solid contaminants from the water by pushing the dirty water through a physical medium.

Mechanical filtration uses physical equipment like sponges, floss, or wool to clean the water. These mechanical filter elements trap solid waste but allow the clear liquid to pass through them.

Mechanical filtration effectively separates the solid waste from the water. However, it does not do anything to contaminants dissolved in the water. Hence, a mechanical filter cannot get rid of toxins like ammonia and nitrite in the water.

Since a mechanical filter traps debris and waste, it gets clogged over time. When the waste fills the filter media, it ceases to operate. Hence, you must clean the sponges and filter media regularly and eliminate the gunk for it to operate continuously.

2. Chemical Filtration

In chemical filtration, chemicals like activated carbon, resins, and charcoal in the filter remove dissolved waste.

The filter media reacts with the contaminants in the water and converts them into a form that can be easily removed.

However, chemical filter media gets used up over time. You will have to replenish it at regular intervals to keep it working continuously.

3. Biological Filtration

Biological filtration relies on nitrogenous bacteria like Nitrosomonas and Nitrobacter to clean toxins in the water.

These beneficial bacteria are introduced into the tank through biological filters. They feed on ammonia and nitrites in the organic waste and leftover feed in the tank. They convert these toxins into less harmful nitrates and make the tank safe for its inhabitants.

While biological filtration is an essential part of tank filtration, it will only act on the toxins present in the water. These bacteria do not do anything to the physical waste that is created in a tank. Hence, you will have to combine it with a mechanical filter for a completely functional filtration system.

So, we can conclude that all three types of filtration are necessary to clean a fish tank properly.

Mechanical filtration will eliminate the physical waste in the water. Meanwhile, biological filtration removes toxins and makes the water safe for fish. Chemical filtration removes dissolved contaminants from the water and polishes it.

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2 Main Categories Of Filters: Internal And External

Regardless of the type of filter media used, we can broadly classify fish tank filters into two main categories based on their placement in an aquarium setting. They are internal filters or external filters.

1. Internal Filters

Internal filters are suitable for small to moderate fish tanks. You must place these filters inside a fish tank.

The tubes in the filter draw the water from the fish tank into the filter compartment. Here, the water will pass through the different filter media and becomes clean. The clean water then returns to the tank through the output tube.

2. External Filters

Large tanks need external filters for thorough cleaning. These filters are bigger than internal filters and hold more filter media.

External filters sit or hang outside the fish tank. They draw water into the filter compartment through tubes and run it through different stages of filtration. The outlet pipes of the filter return the water to the tank.

7 Types Of Fish Tank Filters

Now, let us look at the different types of internal and external filters available in the market.

1. Sponge Filters

Sponge filters are basic filters that use mechanical filtration to clean the water. They have three main parts — a sponge, air pump, and tubing.

The air pump produces air bubbles that push the water into the filter. As the water flows through the filter, the sponge traps the physical dirt and debris. The rest of the water then flows back out of the filter.

Over time, sponge filters will develop a colony of beneficial bacteria. These bacteria perform biological filtration. Thus, a stable nitrogen cycle is established in the tank.

Sponge filters are simple but practical. By physically moving the water, sponge filters keep it well-aerated. However, sponge filters can be noisy.

Additionally, sponge filters will not work once they are clogged. So, you will have to manually clean them for operating them smoothly.

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2. Box Filters

Box filters are compact filters. You can attach these filters to the glass surface with suction cups. These filters carry a variety of filter media.

You can take them apart easily and refill them with different filter media depending on your need. Box filters will usually sit in the corner of the tank and operate quietly.

Due to their small capacity, these filters are usually used for hospital tanks or very small fish tanks with a few fish. Some box filters will need an air pump to move the water into the filter.

3. Canister Filters

Canister filters are suitable for big tanks that hold at least 40 gallons of water. They use a combination of mechanical, chemical, and biological filtration methods to clean the water.

In canister filters, a motor draws water from the aquarium into the filter. It passes through several layers of filter media and is thoroughly cleaned before being returned to the tank.

The water from these filters will have a good flow when it returns to the aquarium.

These filters are good for saltwater aquariums that have higher filtration needs than freshwater aquariums. They are also suitable for tanks with fish that are very sensitive to water parameters as they clean the water very well.

Since canister filters are huge, they are not easy to take apart and clean. However, you will not have to clean these filters too often as they have a large amount of filter media.

4. Fluidized Bed Filters

These are newer filters that use biological filtration to clean the water. They contain sand or silica chips that mechanically filter the water.

Fluidized bed filters are placed on the back of the aquarium. Water passes into the chamber containing the filter media and swirls through it. This churning of water promotes the growth of healthy bacteria and aerates the water.

The agitation process separates the physical waste from the water. Additionally, the bacteria in the filter get rid of the toxins in the water.

You can use fluidized filters alone or with another filter. The only problem with this filter is that it is long and can only be used in tall tanks.

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5. Hang-On Back Filters Or Power Filters

Power filters hang on the back of an aquarium. These are powerful filters with mechanical, chemical, and biological filtration media.

The intake tube of the power filter is immersed in the aquarium. The unit has a motor that sucks the water into the intake tube. The water will then pass through the different filter chambers and becomes clean before returning to the aquarium.

The water from the outlet of the power filter has a high force and strong flow. You can add extra filter media into the compartments of a hang-on filter for added efficiency.

Power filters have a long life span. Hence, they are a good investment if you intend to add more fish to your collection over time.

6. Trickle Filters

Trickle filters are mainly used in saltwater aquariums. Their primary purpose is to aerate the water by exposing it to air. For this, the tank water passes through a container with floss, wool, or plastic balls.

As the water trickles through the container, it becomes clear. The slow movement also promotes aeration and supports the growth of helpful bacteria.

These bacteria perform biological filtration. The filter will also usually have a layer of chemical media for added efficiency. Hence, trickle filters are a complete filtration setup.

The only drawback of trickle filters is that they clog up easily due to the small size of the internal container and need frequent cleaning. You can eliminate this problem by passing the water through a mechanical filter before it reaches the trickle filter.

7. Under Gravel Filters

Under-gravel filters were once very popular but are not too common now. These filters have a plate that must be placed on the substrate.

An air pump drags the water into this plate, and the filter traps the debris and waste in it. There are no chemical filter media in an under-gravel filter.

You cannot use under gravel filters in tanks with live plants as they need space in the substrate. Additionally, they are not easy to maintain. These filters get clogged quickly and need frequent cleaning.

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What Type Of Filter Is Best For A Fish Tank?

You should have a filter in your fish tank as it makes tank maintenance a lot easier and ensures the water is clean and healthy for your fish.

However, it is difficult to recommend a single filter that will work for all fish tanks. Your choice will depend on various factors like whether you have a freshwater or saltwater tank, the size of the tank, the type of fish and plants in it, and the space you have for the tank.

Large tanks need powerful filters to clean the water efficiently. External filters are the ideal choice in this case. A large tank is best cleaned with a variety of filter media. So, filters that accommodate all three methods of filtration are the best choice.

If your fish are very sensitive to changes in water chemistry, you will need a highly efficient filter that preferably has mechanical, chemical, and biological filter media. If the fish produce a lot of waste, you will need a bigger filter to clean the water.

Another factor to consider is the water flow. If you use strong filters for a tank with slow-moving fish, they will struggle against the current. It can stress them out and affect their overall well-being.

You should also pay attention to the purpose of the filter. For small tanks or hospital tanks where you keep sick fish or fry, small filters or soft sponge filters will do.

A small filter will be able to handle this bioload. Additionally, there are fewer chances of the fry getting sucked into the filter when you use a soft sponge filter with few mechanical parts.

Regardless of the type of filter you choose, you will still have to keep it clean for efficient operation. While small internal filters need more frequent cleaning, you can put off cleaning for a bit longer with larger filters. Nonetheless, the cleaning process will take longer for big external filters.

By properly cleaning the filter media and replacing exhausted media on time, you can ensure that your tank stays clean and is a healthy environment for your fish.

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