Do Fish Need a Filter to Survive?

Filtration is an important part of a fish tank. Especially when it is a freshwater fish tank. It makes the water safe and suitable for the fish to live in. But do fish need a filter to survive? Is there any fish that does not need a filter to live?

In general, the answer is, yes. It will be tough for most of the fish to survive without a filter. There are some fish that do not need filtration. Some of them are betta fish, goldfish, guppies, etc.

In this case, there are some important factors you need to know.

Do Fish Need a Filter to Survive
Do Fish Need a Filter to Survive

Why Fish Tank Need a Filter?

It needs a filter so that, there is enough capacity for the tank to maintain biological filtration.

Here bare minimum filtration a fish tank need is biological filtration. Otherwise, the environment of the tank would become toxic very often.

If you can provide biological filtration without a filter in any other way, in that case, your fish can survive without a filter.

But providing biological filtration without a filter is very costly and hard to maintain. So, most people prefer to add a filter for the betterment of the fish as well as for themselves. 

Can a Filter Oxygenate a Fish Tank?

Yes, a fish tank filter helps to oxygenate the water.

Fish need oxygen to breathe just like humans. They take oxygen from the water. In an unfiltered tank, they can take oxygen released from the live plants.

In a tank with a filter, it can oxygenate the water by moving it. A filter works by sucking the dirty water and releasing fresh water. In that process, water moves and dilutes oxygen in it.

The more powerful filter it is or the filter with a higher flow rate can dilute more oxygen. To oxygenate the water, even more, people use water pumps as well as the filter.

The Benefits of Having A Filter

There are many benefits of having a filter in your tank. But the one that should be mentioned first is, it will cause less stress to you as well as your fish.

If you do not add a filter to your fish tank, it is stressful. You need to clean and maintain the tank very frequently. Otherwise, the toxin build-up can harm your fish.

On the other hand, frequent changes in water are not only time-consuming but also cause stress among fish. They like to stay and live in constant water conditions. Which you cannot provide in an unfiltered tank.

A filter will overall increase the water quality and relief you from those extra work.

What is Biological Filtration?

Biological filtration is a process by which the waste released by the fish, in the form of ammonia breaks down and converts into nitrates.

Ammonia builds up in the water and eventually makes the water toxic. This kind of filtration system uses living organisms like bacteria to detoxify the tank water. Those bacteria are also known as beneficial bacteria for the fish tank.

The filter provides the surface to help those bacteria to grow. If you can provide any other surface other than a filter for the bacteria to grow, your aquarium can operate without a filter.

How to Maintain an Unfiltered Tank

The main point here is to keep the water quality fresh and high. A good quality filter helps a lot in this aspect. But maintaining an unfiltered one is not impossible. Here are some basic tips to maintain an unfiltered aquarium.

Live Plants

The first thing is, you need to choose fish that can live not only without an unfiltered environment but also improves the ecosystem. You have to put a lot of plants in this regard. Live plants will convert the CO2 to oxygen for the fish.

Frequent Water Change

The second thing is frequent water changes. With a filter, it is enough to change the tank water every two weeks. But if are keeping the tank without a filter then you need to change the water more frequently.

Reduced Algae Growth

In this kind of aquarium reducing the algae growth is also important. Live plants will help you to keep the algae growth rate low. Another thing you can do is keep the fish tank in a low-light area of the house. Because excessive light, especially sunlight increases the growth of algae.

Know the Additives

Be careful about what you put into the tank. Any kind of water fertilizer or other chemicals can change the chemical reaction in the aquarium. Once it has changed it is not easy to get the water condition back.

Best Fish to Keep in an Unfiltered Fish Tank?

You have to be very careful while choosing the fish for an unfiltered tank. Not all fish can do well in this kind of situation. Here are some fish you can keep without worrying much.

1.  Fancy Guppies (Poecilia reticulate)

Guppies can be your first choice for an unfiltered tank. They are small fish of about two inches but hard enough to survive without a tank. They prefer warmer temperatures. So, you might need a heater for them.

2. Neon Tetras (Paracheirodon innesi)

Another popular fish is known for their hardy nature and vibrant color. They grow around one inch and prefer acidic water. The temperature needs to be on the cooler side for them.

3. Paradise Fish (Macropodus opercularis)

This one also comes with vibrant colors. Can live in warm or cool water as they can survive water fluctuation. Very hardy in nature, grows around two inches.

4. Common Plecostomus (Hypostomus plecostomus)

It can be a short-term addition to your tank as they are well-known fish to clean the tank. They eat algae and reduce algae growth significantly. But as they grow bigger, they need to move to a filtered tank.

5. Bronze Corydoras (Corydoras aeneus)

Bronze corydoras are bottom eaters. Another great addition to keep the tank clean. But be careful if you chose these fish. Because they do not have scales and are prone to additives. Do not randomly add additives to your unfiltered tank.


There are various kinds of fish you can keep in your fish tank. some of them are hardy and some of them are sensitive. Hardy fishes can survive without a filter.

But keep in mind that, you just do not need your fish to survive. You only can see their true potential and beauty when they will thrive in the tank. A filter will help you in that aspect.

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Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

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