Do Betta Fish Need A Filter: The 4 Main Benefits

Last Updated on 2023-08-13

It used to be a common belief that bettas could live in a small bowl without any heater or filter and be completely fine. And while there are rare circumstances where a betta doesn’t need a heater or filter, the chances are extremely slim, and it will take a lot more work on your part. So do bettas need a filter? Definitely!

But if you keep reading you’ll find out the different types of filters there are, as well as what they do. You’ll also find out the main reasons why filters are so important, what to do if you don’t have a filter, and what happens if you decide not to use a filter in your tank as well.

Do Betta Fish Need A Filter?

The main purpose of a filter is to keep the tank clean. Without a filter, you’ll notice over time your bettas water becomes cloudy. But it’s not what you see that’s dangerous, it’s what you don’t see.

Millions of harmful bacteria will begin to reproduce rapidly in your tank. And the stress of the dirty water will weaken your bettas immune system, making him more susceptible to catching a disease.

In nature, it’s very hard to find fish that live for large amounts of time in water that has never been naturally filtered. This is because filtration is a part of the delicate balance that helps everything grow and thrive.

So to answer the question

Bettas need a filter. If you keep your betta in a tank without a filter, then bacteria and ammonia are likely to spike out of control. Weakening your bettas immune system, stressing him out, and even causing death. Frequent water changes aren’t enough to replace the benefits a filter has in a tank.

So while you may have heard that bettas can survive in dirty water as it’s similar to rice paddies, and ponds that make up their natural habitat, this isn’t true. In fact it’s incredibly dangerous advice.

Why Do Bettas Need A Filter?

Filters are there to keep your tank clean from any debris such as decaying matter, feces, rotten food, chemicals, and harmful bacteria. As you can see there are a lot of harmful substances in your tank that need to be removed for the sake of your betta.

Your filter removes these dangerous substances by sucking in water and passing it through a variety of different media and sponges. Once the water has passed through everything it will be clean and safe for your betta.

Even though water changes are still necessary with a filter, you won’t have to do them as often. Which is definitely a nice bonus.

Reasons To Use A Filter In Your Betta Tank

Here are all the reasons a filtered tank is so essential for keeping your betta healthy and happy! Remember, without them, your betta is likely to suffer a reduced lifespan.

Removing Ammonia, Nitrites, And Nitrates

The most important reason you’re going to need a filter in your betta tank is to stop a build up of ammonia, nitrites, and nitrates. When any of these build up too much in your tank it’s going to spell bad news for your betta. Ammonia especially will stress out your betta and weaken his immune system. In fact, if left too long ammonia will kill your betta. (Commonly known as ammonia poisoning.)

The good news is that sponges in your filter will harbor helpful bacteria which feed on ammonia, nitrites, and nitrates. And as long as there are enough helpful bacteria, the levels of all three will remain safe. While the bacteria can also be found in your tank, it’s still going to grow in abundance in your filter.

Moves Water Around

Water that isn’t being moved around will quickly become stagnant. When water is left to stand for too long carbon dioxide from the air begins to be absorbed. This carbon dioxide is not only bad for your betta, but it’s also going to affect the pH in your tank. While this can be overcome with an air stone, it’s still a lot more practical just to use a filter instead.

Oxygenates Your Tank

Water not being stagnant isn’t the only benefit you’re going to get from using a filter. The movement is also going to oxygenate your tank. This isn’t as important to bettas who have a labyrinth organ (an organ that allows them to breathe from the surface of the water). But it is important to any other fish you have in your tank as well as the plants.

You Won’t Have To Perform Water Changes As Often

Just like previously mentioned if you have a filter in your tank you aren’t going to have to perform water changes as often. The main reason you need to change your water is that it helps to remove any harmful bacteria and chemicals, as well as diluting any that are already in your tank. Because a filter also does this it means you won’t have to change the water as often.

However, it is still necessary to change it. Without frequent water changes none of the vital minerals and nutrients that your betta needs will be replenished. Without any water changes, your betta will suffer over time!

All of these are great reasons for you to make sure you have a filter for your betta.

Do Betta Fish Need A Filter Infographic

What Happens To Your Tank Without An Aquarium Filter?

Without an aquarium filter, your betta will be able to survive for a time. And if you do frequent water changes then you can extend this time even more. However, you can expect your bettas life to be cut drastically if you choose to not have a filter in your tank.

First of all, without a filter, the water is never going to be as clean. And the constant water changes you’d need to keep the water as clean as possible would stress your betta out. Not to mention that it would also create massive amounts of instability in your tank. Without a culture of good bacteria being able to grow in your tank, the water parameters in your tank would be impossible to control.

As well as this, the water in your tank won’t be oxygenated, and it will quickly become stale. This is also going to cause your betta to become sick and may make your house smell a little unpleasant.

And of course, any harmful chemicals will just stay in your tank. Over time they will become more and more diluted as you perform more water changes, but they’re going to be dangerous the whole time they’re in your tank.

What Are The Different Filtration Methods?

In your filter, there are three main filtration methods that will keep your water clean. They are Mechanical Filtration, Biological Filtration, and Chemical Filtration. Mechanical Filtration removes any debris and dirt that can build up in your tank, Biological removes any harmful bacteria, and chemical removes any harmful chemicals. Here’s some more information about the different methods.

Mechanical Filtration

Mechanical filtration is the one that you’re going to notice the most. It’s the one that removes all noticeable debris from your tank. However, it’s important to remember that mechanical filtration on its own isn’t going to truly keep your tank clean. Instead, it’s going to help it LOOK clean.

Mechanical filter cartridges should be replaced every 2-4 weeks depending on the size of the tank and filter. If you don’t change your mechanical filtration cartridge often enough you will begin to notice a decrease in water flow. This is because water will have a hard time passing through a cartridge that is too clogged up with debris.

Chemical Filtration

Chemical filtration is going to do exactly what it implies. Filter out any harmful chemicals that shouldn’t be in your betta’s tank. It’s most commonly activated charcoal that is used for chemical filtration.

Activated charcoal is charcoal that has been heated up. Once it’s been heated it is able to absorb more, allowing it to do a better job of absorbing any chemicals.

However, with how technology is improving rapidly, there are a number of different chemical filters you can buy, and they all target different types of chemicals. If you’re a novice betta keeper, you don’t need to worry about them too much now. Instead, just stick to whichever one comes with your filter!

Biological Filtration

Unless there’s a large number of chemicals in your tank (which there shouldn’t be), your biological filter is the most important one for the health of your betta.

Biological sponges allow helpful bacteria to live in your tank. These bacteria are vital to the nitrogen cycle and help break down decaying matter to a point where it’s no longer harmful to any fish or plants in your tank.

A Brief Guide To The Nitrogen Cycle

If you’re not sure about the nitrogen cycle then here’s a quick guide which will help you have a clear understanding of what’s going on in your tank.

  1. All waste products in your aquarium are broken down by bacteria and fungi into ammonia. This includes dead organisms, decaying food, feces, dead plants and anything biological. (Ammonia is poisonous to everything in your tank, and should be at 0ppm or 0 parts per million.)
  2. Nitrosomonas (another bacteria) breaks down ammonia into nitrite. While nitrites aren’t as harmful they can still do a lot of damage to anything in your tank. So once again it’s important for the nitrite levels in your tank to be 0ppm.
  3. And then another bacteria called Nitrobacter breaks down the nitrite into nitrates. Nitrates aren’t as harmful to fish and you only need to make sure the levels of nitrate in your tank are below 20ppm. You should be warned though that higher nitrate levels are responsible for algae blooms.
betta fish image 1

For the nitrogen cycle to be successful you need enough areas for bacteria to grow. This is what your biological filtration system is for. As well as any large areas in your tank such as the substrate and ornaments.

When picking a biological filter there are two main components.  First of all the more surface area, the more bacteria it’s going to be able to hold. And secondly, the more oxygen that’s going through the filter the more bacteria can grow. All of the bacteria in the nitrogen cycle thrive on oxygen.

For best results, you should have a large biological sponge that’s exposed to the air. This way you’re going to get the maximum amount of oxygen into the sponge and the biggest surface area possible.

do betta fish need a filter

Different Types Of Filters

As you can see filters are an important aspect of any tank, and one piece of equipment any serious betta keeper will want to have. But, luckily, there’s not just one filter for you to use. There are so many different ones to choose from. Each one has its pros and cons.

HOB Filters

HOB filters or hang-on-back filters are the filters you see hanging on the back of aquariums. They are the most commonly used filters and the best part is they provide all the different types of filtration that you need. If you’re just getting started the power filters are a great first filter.

As well as coming with all the three types of filtration they also come with a siphon that sucks water into the filter. As the water flows through your filter media it will be cleaned and pumped back into the water. This has the added benefit of creating water flow as well.

One of the biggest drawbacks to power filters is the need for the cartridges to be changed or washed regularly. You’ll notice that debris will begin to block up your filter if you don’t wash it enough, and that’s why the cartridges should be regularly changed as well.

But of course, how often you have to do this is going to depend on the quality of your filter.

And try to look for a HOB filter with a biowheel as well. Biowheels are wheels that spin as water passes them. They will be partially out of the water, so each part of it will be in contact with the air at some point. This allows for massive amounts of bacterial growth in a very large area of space.

If you’re new to betta keeping then HOB filters are going to be the best place for you to start.

Internal Filters

Another great choice are internal power filters. And as you can guess by the name, they are placed inside your aquarium. Normally you can mount them to the wall with a suction cup but you can also lay them across your substrate. In fact, a lot of betta owners do this to suck up any debris right away.

Normally internal filters will require an airline from outside the tank with a pump. Air is pumped through the bottom of the filter through the cartridge and then air bubbles and clean water are released from the top of the filter.

There are also two main types of internal filter. Sponge Filters and Corner Filters.

Corner Filters

Corner filters are placed in the bottom corner of your tank and an air pump is used to pump water through them. They are able to perform all 3 types of filtration, however, due to the low oxygen content, and the smaller amount of water that passes through them they aren’t as effective as some other filters.

The benefit of corner filters is that they are small and discreet. They can work great in smaller tanks, so if you’re housing a betta on their own then you could consider a corner filter.

Sponge Filter

Again, if you have a smaller tank, or you’re only housing your betta on his own then a sponge filter might be the right choice for you. They’ll need an air pump to draw oxygen and water through and because of this, they aren’t going to be as efficient as power filters.

The sponge material in sponge filters is able to provide mechanical and biological filtration, however, in most cases, you’ll also have to add another media for chemical filtration.

There are two areas where sponge filters really excel. In quarantine tanks and breeding tanks.

In a quarantine tank, you won’t have to worry about medication being filtered out because there is no chemical filtration. And because of the fact, there’s no strong flow coming from sponge filters you won’t have to worry about any fry being sucked into the filter.

You should rinse the sponge every week with aquarium water from your tank. This is going to remove all the debris that’s stuck in it, without destroying all the beneficial bacteria!

Sponge filters are also some of the best choices for your betta as they’re a lot more gentle, meaning you won’t have to worry about your bettas fins getting damaged. The biggest downside of course is trying to find a place for activated carbon however.

If You’re Interested In Sponge Filters Here Are The 6 Best Options


Undergravel Filters

Undergravel filters are great if you want your filter to be discreet and not seen in your tank. This filter works by multiple uplift tubes that are pointed towards the surface of the water. When an airstone or powerhead is placed on top of the tubes water begins being sucked through the gravel.

The gravel then acts as a mechanical and biological filter. Any debris that is in your tank will be sucked into the gravel where it becomes stuck. And due to the oxygenation from the airstone occurring on all the gravel, it becomes a great place for bacteria to grow.

One of the biggest flaws of under gravel filters is the inconsistency. Because water can flow through different spots at different rates, some spots will harbor a lot of debris which you will need to vacuum out with a gravel vacuum. If you don’t do this then pockets of hydrogen sulfide can end up in your tank, which will eventually poison your betta.

So if you’re looking for something discreet and you don’t mind the extra work required with under gravel filters, then they can make a great filter for your tank.

And if you have a planted aquarium it may be better to avoid undergravel filters. The constant cleaning your gravel will require, as well as disturbance from the filter itself, may have a negative effect on your plants.

Canister Filters

If you have a large aquarium that houses your betta and other fish, then you’ll want to get a canister filter. While power filters are good for smaller tanks, when you get to 30 gallons+ a canister filter will do the job a lot better. Most times they are placed underneath your aquarium.

Canister filters work by removing water from your aquarium into an external filter. The strong pressure pushes water through different filter media, and once it’s gone through the clean water is pumped back into the tank. Because of the high pressure, canister filters are extremely efficient and effective ways of keeping your tank clean.

However, canister filters are also going to require more maintenance than regular filters. Because there are a lot more tubes and the filter itself is external, you’re going to have to clean a lot more parts and make sure that everything is working perfectly.

If you want to master Betta fish care in no time, check out this article!

What’s The Best Filter For Bettas?

If you have a small tank, then sponge filters or HOB filters are going to be the best choice for your betta. Remember you need a tank that’s 5 gallons or bigger to ensure that the ammonia, pH levels, and temperature in the tank don’t fluctuate too wildly.

The fish tank filter I’d definitely recommend for tanks up to 10 gallons is the Aquaclear 20 Power Filter. It’s the best filter at this size, thanks to the fact it can sit outside of your aquarium and it also has an adjustable flow rate so you can ensure it doesn’t blow your betta around.

AquaClear 20 Power Filter, Fish Tank Filter for 5- to 20-Gallon Aquariums
  • Aquarium filtration system that offers superior contact time with filter media and energy efficient pump lowers operating costs
  • Quick and easy installation; we recommend that you clean aquarium filter every 2 weeks for maximum operation and efficiency
  • Provides optimal mechanical; chemical; and biological filtration
  • Comes equipped with AquaClear Foam; Activated Carbon Filter and BioMax and Cycle Guard for superior water quality
  • Filtration volume is up to 7 times larger than comparable fish tank filters

If you can’t get your hands on the Aquaclear for whatever reason, I’d go for the Aqueon QuietFlow in it’s place.


Here are some more frequently asked questions on why betta fish need a filter!

How Long Can A Betta Fish Live Without A Filter?

Betta fish are quite resilient, but even so, without a filter their lifespan will shorten dramatically. While it is possible for them to survive a long time without a filter, this will require frequent water changes, and it’s still harmful to them.

How To Care For A Betta Fish Without A Filter?

If you don’t put a filter in your bettas tank, then you’ll need to perform frequent water changes. Depending on the tank size, you should change about 10-30% of the water every few days. This keeps the ammonia levels low, a crucial factor as too much ammonia in the tank can be fatal.

How To Setup A Betta Fish Tank Without A Filter?

When setting up a betta fish tank without a filter, add gravel to the bottom of your tank for beneficial bacteria to grow on. Add live plants to absorb extra waste and if possible bottom feeders like shrimp or corydoras. And lastly, make sure you’re performing frequent water changes to keep the ammonia levels low.

Why Is Your Betta Staying By The Filter?

If your betta is hanging out by the filter, it may be due to several reasons. High water current might be stressful, and the input of the filter is normally less strong than the output, so they feel safe there. They could also be unwell and using the filter to stay buoyant.

What To Look For In A Filter For Your Betta?

All of these filters can be a great addition for your betta tank, but when choosing a filter here are some things that you should look for.

  • Biological, chemical, and mechanical filtration – If your filter doesn’t have all three types of filtration then it is more likely that your betta is going to become sick. While biological and mechanical filtration are a must, you never know what chemicals could be in your bettas water. So it’s always safer to have chemical filtration as well, just in case.
  • Slow water flow – If the current caused by your filter is too powerful it’s going to push your betta around. Bettas like slow flowing water, and if the water current is too strong they’re going to get stressed out. Make sure you purchase a filter that has a slow current, or even better an adjustable current.
  • Easily cleaned and maintained – You want to have a filter which you can clean easily. As well as this, you should also have one with easily removable filter media. If you’re spending a lot of time trying to remove filter media then you’re going to stress your betta out. You should try to find a filter where you can remove and replace the media with minimal effort.
  • Reliable – And of course, you’re going to want a filter that is reliable. Without a reliable filter then you’re putting your betta’s health at risk. It’s worth paying a little extra for a filter you know is going to get the job done and last a long time!


There is a LOT of information on this page. It can be hard to remember it all. So to make it easier here are some of the most important points to take away.

  • Betta’s most certainly need a filter if you want them to live a long and healthy life. You can get by for some time without using a filter, but it will decrease your betta’s lifespan dramatically and it’s also going to ruin their quality of life.
  • Filters remove any dangerous substances whether they’re chemical, bacterial or physical.
  • The three main filtration methods are mechanical filtration (removing debris and physical contaminants from the tank), chemical (removing any chemicals that may be in the water), and biological (healthy bacteria that remove ammonia, nitrite, and nitrates as well as removing any harmful bacteria from the tank).
  • Without an aquarium filter, your aquarium water will begin to look cloudy and dirty. However, this is the most superficial problem. The water will also become more and more poisonous to your betta until it eventually kills them.
  • If you don’t have a filter you’re going to have to perform water changes all the time. The amount of time you have to change the water will stress your betta out and stop any helpful bacteria from being able to grow in your tank.
  • There are many different filters you can choose from including power filters, internal filters, canister filters, and undergravel filters. Each of them has its own pros and cons.
  • When picking a filter try to find one that doesn’t cause a strong current, that’s easy to maintain and clean, that is going to be reliable and has all three types of filtration!

If you’re want to know more about how to betta tanks and how to set them up then check out the Betta Fish Tank Setup Guide or this helpful article on EVERYTHING your betta needs!

Ultimate Betta Fish Care Guide
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