Fishkeeping FAQ's

What Type Of Filter Should I Use For A Freshwater Tank?

You’re a freshwater fish enthusiast, eagerly setting up your very own tank. As you prepare to bring your finned friends home, you’re faced with an important decision: what type of filter should you use? With the multitude of options available, it can be overwhelming.

Rest assured, we’re here to help you navigate through the choices and find the perfect filter to provide a clean and healthy environment for your aquatic companions.

From sponge filters to hang-on-back filters, we’ll explore the pros and cons of each, ensuring that you make an informed decision for your freshwater tank.

Types of Filters

When it comes to setting up a freshwater tank, choosing the right filter is essential for maintaining a clean and healthy environment for your fish.

There are several types of filters available on the market, each with its own unique features and advantages. Let’s take a closer look at some of the most common types of filters you can consider for your tank.

Sponge Filters

Sponge filters are a popular choice among freshwater fishkeepers, especially for smaller tanks. These filters work by drawing water through a sponge, which acts as both a mechanical and biological filter. The sponge traps debris and provides a surface area for beneficial bacteria to grow, aiding in biological filtration.

One of the advantages of sponge filters is their gentle water flow, which is ideal for delicate fish species such as fry or bettas. Additionally, sponge filters are relatively inexpensive and easy to maintain. However, they may not be suitable for larger tanks or tanks with high fish loads, as their filtration capacity is limited.

Hang-On-Back (HOB) Filters

Hang-on-back filters, also known as HOB filters, are another popular and versatile option for freshwater tanks. These filters are designed to hang on the back of the aquarium, with a water intake tube that draws water into the filter and a return tube that expels filtered water back into the tank.

HOB filters typically consist of mechanical, biological, and chemical filtration components. They are capable of handling larger tanks and higher fish loads compared to sponge filters. One of the advantages of HOB filters is their ease of use and maintenance. They are also relatively affordable and widely available.

However, HOB filters can be more prone to noise compared to other filter types, especially if the water level drops too low. It’s important to regularly clean and replace the filter media to ensure optimal filtration efficiency.

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Canister Filters

Canister filters are considered to be more advanced filtration systems, capable of handling larger tanks and providing superior filtration performance. These filters consist of a canister that is placed underneath the aquarium, which houses various filtration media such as mechanical sponges, activated carbon, and biological media.

Canister filters offer a high level of filtration customization, allowing you to tailor the media to suit your specific needs. They are known for their exceptional mechanical and biological filtration capabilities, making them a great choice for tanks with a heavy fish load or sensitive species.

One of the disadvantages of canister filters is their higher initial cost compared to other filter types. They also require more regular maintenance and can be more challenging to set up initially.

However, if you are willing to invest in a reliable and efficient filtration system, a canister filter might be the perfect choice for your freshwater tank.

Internal Filters

Internal filters, also known as submersible filters, are a compact and space-saving option for freshwater tanks. These filters are designed to be fully submerged in the aquarium, providing mechanical and biological filtration.

Internal filters typically consist of a motor-driven pump, which draws water through a series of filter media before returning it to the tank. They are suitable for tanks of various sizes and can handle moderate fish loads.

One of the advantages of internal filters is their ease of installation. Since they are fully submersible, they do not require any additional space outside of the tank. They are also relatively quiet during operation and can provide a decent level of filtration efficiency.

However, internal filters may not be as effective as other filter types when it comes to larger tanks or tanks with high fish loads. They also tend to take up some space inside the tank, which can be a drawback for aquascaping or decorating purposes.

Undergravel Filters

Undergravel filters are a traditional and simple form of filtration often used in smaller freshwater tanks. These filters consist of a plastic, slotted plate that is placed at the bottom of the aquarium, usually covered with a layer of gravel. Water is drawn through the gravel, creating a natural filtration process.

Undergravel filters primarily provide biological filtration, promoting the growth of beneficial bacteria in the gravel bed. They can be an affordable option for smaller tanks and can be easily installed without any additional equipment.

However, undergravel filters have some disadvantages. They can be less effective at removing debris and waste compared to other filter types. The gravel bed can also become a breeding ground for harmful bacteria if not properly maintained.

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Additionally, undergravel filters may not be suitable for tanks with live plants, as the roots can get tangled in the gravel.

Fluidized Bed Filters

Fluidized bed filters, also known as sand filters, are a unique type of filtration system that uses sand or other small media to create a continuous flow of water. These filters work by suspending the media in a column, allowing bacteria to thrive and break down organic matter.

Fluidized bed filters are known for their exceptional biological filtration capabilities. They are particularly effective at removing dissolved organic compounds and ammonia from the water. They are also relatively compact and can be suitable for medium-sized tanks.

However, fluidized bed filters can be more expensive compared to other types of filters. They also require careful monitoring and regular maintenance to prevent clogging and maintain optimal filtration efficiency.

Trickle Filters

Trickle filters, also known as wet/dry filters, are commonly used in larger freshwater tanks or high-load aquariums. These filters consist of a chamber filled with bio-media, where water is trickled over the media, allowing for efficient oxygenation and biological filtration.

Trickle filters are known for their exceptional biological filtration capabilities and handling large fish loads. They provide a large surface area for beneficial bacteria to colonize and can effectively remove ammonia and nitrites from the water.

One of the advantages of trickle filters is their ability to maintain stable water parameters, especially in heavily stocked tanks. They are also relatively quiet during operation and can be installed outside of the tank, saving valuable space.

However, trickle filters can be more expensive compared to other filter types, especially for larger tanks. They also require regular maintenance to prevent clogging and ensure optimal filtration efficiency.

UV Sterilizers

UV sterilizers are not filters in the traditional sense but are often used in conjunction with other filtration systems to maintain water clarity and prevent the growth of harmful bacteria and algae. These devices use ultraviolet light to kill or deactivate any microorganisms that pass through them.

UV sterilizers are particularly effective at controlling green water algae and harmful pathogens in the water. They provide an additional layer of protection and can be beneficial in tanks with a history of disease outbreaks or persistent algae problems.

However, UV sterilizers are not necessary for every freshwater tank and should be used selectively based on the specific needs of your aquarium. They can be expensive to purchase and operate and may not be effective against certain types of bacteria or parasites.

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Considerations for Choosing a Filter

Now that we have explored the various types of filters available for freshwater tanks, it’s important to consider certain factors before making a final decision. Here are some key considerations to keep in mind when choosing a filter for your tank:

Tank Size

The size of your tank plays a crucial role in determining the appropriate filter type and capacity. Smaller tanks may work well with sponge filters or HOB filters, while larger tanks may require canister filters or trickle filters to handle the higher volume of water.

Fish Load

The number and size of fish in your tank contribute to the overall waste production and filtration needs. Tanks with a higher fish load will require a more robust filtration system to maintain water quality.

Type of Fish

Certain fish species have specific filtration requirements. Some species, such as bettas or delicate invertebrates, prefer gentler water flow and may thrive with sponge filters or internal filters. Others, such as cichlids or goldfish, require more powerful filtration to handle their waste production.

Mechanical Filtration Requirements

Consider the level of mechanical filtration your tank requires. Some filters offer multiple layers of mechanical filtration media to remove debris and waste more effectively.

Biological Filtration

Efficient biological filtration is crucial for maintaining a stable nitrogen cycle in your tank. Choose a filter that provides ample surface area for beneficial bacteria to grow and thrive.

Chemical Filtration

If you consistently face issues with water clarity or chemical imbalances, consider a filter that includes chemical filtration media, such as activated carbon, to adsorb impurities.


The appearance of the filter in your tank can impact the overall aesthetic appeal. Choose a filter that blends well with your tank design and can be easily concealed if desired.

Noise Level

Some filters can be noisy during operation, which can be bothersome, especially in bedrooms or quiet living spaces. Consider the noise level of the filter and choose one that fits your preferences.

Ease of Maintenance

Regular filter maintenance is essential for optimal performance. Consider the accessibility and ease of cleaning or replacing filter media when choosing a filter.


Budget is an important consideration. Filters vary in price, and it is important to choose one that fits within your budget while still meeting the filtration needs of your tank.

By considering these factors, you can make an informed decision and choose the most suitable filter for your freshwater tank. Remember, maintaining a healthy and clean environment for your fish is key to their overall well-being and longevity.


Passionate fishkeeper. Nature lover. Creative thinker. Music junkie. Adventurer.

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