Aquarium Filter Types

aquarium filters

An important part of aquarium water care is making sure your water ecosystem is within safe parameters, crystal clear and free of debris that can negatively impact your water quality. Things that can harm your aquatic habitat include excess algae, food and aquatic life waste. Fortunately, an aquarium water filter can help keep your pets’ environment clean and can be used in combination with other solutions like aquarium water conditioners and additives.

Water filters help provide stable water conditions for your aquatic life; you’ll want to select an aquarium filter system that fulfills the care needs of the aquatic life you’re parenting. Let’s talk about the kinds of water filter media and the types of aquarium filters available.

Types of filtration media

While there are three common methods for filtering aquarium water, some of the best aquarium filters combine all three into one device. There are also a variety of solutions available for achieving each type of filtration, so pet parents can choose which type fits most appropriately with their aquatic life’s needs.


Biological filtration happens when you introduce and develop populations of nitrifying bacteria into your aquarium. These beneficial bacteria convert toxic ammonia and nitrites into nitrates, which are less harmful to aquatic life. You can use a variety of porous bio-media, such as ceramic bio-rings, to encourage biological filtration in your habitat. Keep in mind that biological filtration is often combined with other types of filtration for additional water care—especially if you have a heavy biological load or dense population of aquatic life.


This method of filtration involves using chemical filter media to remove harmful waste and dissolved compounds from your aquarium’s water supply. Chemical media can take a variety of forms, such as zeolite, ferric hydroxide or resin. However, one of the most common types of chemical filter media is activated carbon. Utilizing activated carbon within a mechanical filtration system can remove a variety of impurities from your water. Keep in mind chemical filtration can also absorb beneficial supplements and some water additives. Activated carbon is extremely helpful when removing medications after treatment, but be sure to remove any chemical filtration media before administering medications.


Mechanical filtration is considered a necessity in most aquatic habitats. This type of filtration physically filters particulates, dirt and debris from the water. A mechanical aquarium filter may come in the form of a sponge, floss, or bonded filter pad. Keep in mind that this type of filtration catches and traps the floating debris but won’t get rid of things like harmful ammonia buildup from fish waste. This is why mechanical filtration systems are often combined with a biological and or chemical aquarium filter system.

Types of aquarium filters

As many types of filtration media there are for aquariums, there are even more options when it comes to the variety of filters that provide biological, chemical and/or mechanical filtration solutions. The following types of aquarium filtration systems are uniquely designed for different size freshwater or saltwater aquariums, providing aquatic species pristine and stable water conditions.

Canister filters

These filters sit outside the aquarium—usually in a stand, cabinet, underneath or on the back of the aquarium. These near-silent filters offer a powerful filtration option for your aquarium. Canister filters are pressurized to force water through filter media and can utilize all three types of filtration. You may spend more on this type of filter than many other options—but they’re also a great option for aquariums larger than 40 gallons. Since they employ pressure and can house large amounts of filter media, they can typically filter larger amounts of water in a shorter time than other types of aquarium filters.

Internal filters

An internal filter sits inside of an aquarium and is fully or partially submerged in water—typically in the corner, attached with suction cups, clipped to the edge or sitting at the bottom of the habitat. One type of internal filter uses a separate air pump that blows air into the bottom of the filter and draws water through the filtration media. This simple solution can be quite adept at mechanical and chemical filtration with the use of filter floss and activated carbon. They’re typically more appropriate for smaller aquariums.

Power filters

A power aquarium water filter is also called a hang-on-back filter. As you might guess, this type of filter hangs on the back of your aquarium. Power filters might be the most common aquarium filter selected, and they can be used on aquariums of nearly any size. A power filter uses a motorized impeller to suck water from the aquarium into the filter body through a siphon hose. The water then passes through mechanical filter media and activated carbon, plus any other chemical filtration media you choose to add. Some power filters even contain bio-media. After passing through the filter media, the water flows back into the aquarium. Hang-on-back filters are sometimes considered the best freshwater aquarium filter available by pet parents.

Undergravel filters

This type of aquarium filter involves putting a slotted plate beneath the substrate in your habitat. Using an air pump or powerhead, oxygenated water is drawn through and filtered by your substrate, then pushed upward through uplift tubes to the top of your aquarium. Waste is collected in the substrate, which serves as food for nitrifying bacteria for any plants rooted there. While this type of filtration can be more affordable than other filter types, it primarily focuses on biological filtration.

Sponge filters

Relatively easy to use, sponge filters provide mechanical and biological filtration. However, this filter type tends to take up some space inside your aquarium. A sponge is connected to a tube with an air pump or powerhead on the other end. The air bubbles (or a mechanical pump) draw water through the sponge, which catches debris and helps clean the water. However, sponge filters do not provide chemical filtration.

Live aquarium plants

If you want to give your aquarium a more natural or decorative look while providing enhanced filtration, live plants are a great option to supplement your main filtration system. They take in ammonia, nitrites and nitrates, using them to grow and thrive. You will not only be creating a natural ecosystem that filters out contaminates from your aquarium, but you’ll also be creating a beautiful environment with the addition of live plants.

Is a filter necessary for my aquarium?

Yes. An aquarium filter system is considered necessary to provide a happy, healthy aquatic habitat. Aquatic life forms naturally produce waste and ammonia as they feed and breathe. Without proper filtration, these contaminants will accumulate, creating a toxic environment for all aquatic life.

How does a filter keep my fish tank clean?

Some of the best aquarium filters do their job without you noticing—so you might not even realize all the hard work they’re doing. While water flows through the filter, it catches dirt and debris and absorbs contaminants. The clean water is returned back into your aquarium, while the particulates and contaminants remain trapped on or in the filter media until you clean or change it.

Can I filter an aquarium too much?

It’s unlikely you’ll ever filter too much debris or waste from your aquarium. Filtration naturally catches waste and releases the rest of the water back to the environment. Since the point of aquarium filtration systems is to remove harmful elements, you can’t trap too many of them.

While it’s not likely you’ll over-filter your aquarium, a filter that is too large can create strong water flow within your habitat. Some types of aquatic life don’t tolerate rapid water flow very well, which causes stress. You also need to make sure your filter system’s suction isn’t so powerful that it will harm or trap small aquatic life. Use an aquarium water filter meant for your aquatic life’s species and habitat size.

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Reviewed by Dawn Burch, Director of Animal Care, Education and Compliance (ACE) Team

Dawn is Petco’s Director of Animal Care, Education and Compliance, leading a team that supports animal care operations, regulatory compliance, learning and development, veterinary relations and more. She is passionate about animals and committed to improving the lives of our companion animals, aquatic life, guests and partners.