Last Updated: January 24, 2023 by Flora Gibbins
Betta fish are famously ferocious species primed by nature for survival. They’re often sold without an aquarium filter in a one-gallon tank.
In their natural habitat…
Betta fish can survive without artificial filtration and in small water pools because their labyrinth organ allows them to breathe atmospheric air directly. Their natural habitats are typically more contaminated than your average betta fish tank and they rely on droughts and rainstorms to change their dirty water.
But in a controlled environment, do betta fish need a filter? It turns out the answer isn’t so simple, so stick around as we explain what filters do and whether bettas need them.
- The Short Answer
- What Happens to an Unfiltered Tank?
- What Do Aquarium Filters Do?
- Why Should I Use a Filter in My Betta Tank?
- Can Betta Survive Without a Filter?
- Water Filtration Methods
- Types of Filters
- How to Pick a Filter for Bettas (And Other Tropical Fish)
- Watch This!
- Frequently Asked Questions
The Short Answer
Betta fish need an aquarium filter to clear the water of any waste, such as debris, rotten or uneaten food, feces, and toxic particles. But another critical benefit of filters is improving water quality by cycling the water. The filter oxygenates the water and keeps its pH levels stable.
In theory, your betta fish can live without a filter if you can consistently manage to optimize the water for it.
However, this will require a lot of fish-keeping effort on your part. You’ll need to do constant water changes and introduce helpful bacteria to feed on your fish’s waste. Also, you’ll have to use an air stone to stir up the water gently. And even then, it’s safer for the fish if you use a water filter.
What Happens to an Unfiltered Tank?
If you leave your betta fish in a smaller tank without filter media, it won’t lead a long and healthy life unless you change its water frequently. And even if you do, your betta might die abruptly if the water is too dirty at some point.
That’s because the aquarium water will always be dirty without any filter media. And as it runs out of oxygen, the water will turn stale.
And yes, bettas can breathe air through their labyrinth organs, but they can’t rely on it solely, so the tank water must be oxygenated.
You can work without a filter for a while if you’re ready to change the water frequently. However, this takes a toll on the easy-to-aggravate betta fish, especially with the amount of instability frequent water changes create.
After a while, copious amounts of stress are dangerous to your betta fish. And when combined with fish waste, it can be lethal.
What Do Aquarium Filters Do?
As the betta lives its life in the aquarium, wastes build up in the bottom. Leftovers, debris, rotten food, feces, harmful chemicals, and bacteria accumulate in the tank and can spread throughout over time.
Toxic substances like ammonia and nitrates are infamous betta killers that rarely make it into filtered betta tanks. And since these particles are tiny, you need a filter to remove them.
The primary job of filter media is to catch these harmful particles and trap them away from the natural water flow.
An air pump filter can also aerate slow-flowing water, making it easier for bettas to breathe. You’ll still need to do constant water changes even with a filter. But you don’t need to do them nearly as much. For example, you could go from needing to change the water daily to once every 1-2 weeks.
Why Should I Use a Filter in My Betta Tank?
The most important reason to use an aquarium filter is to eliminate the buildup of toxic substances like ammonia, nitrates, and nitrites. These chemicals often build up in fish tanks and can lead to poisoning and eventual death. Ammonia is prone to spiking a betta tank if it’s not cleaned promptly.
Bettas live with other fish and beneficial bacteria that feed on waste in natural habitats. However, if your betta fish lives alone, you need to give it a filtered tank.
Using a sponge filter is a great way to eliminate toxic substances since it promotes the growth of these helpful bacteria that feed on ammonia, nitrates, and nitrites. Another essential reason to use aquarium filters is to stir up the water flow.
If the water becomes too still, it absorbs carbon dioxide from the air, which replaces the oxygen in air bubbles. Unfortunately, this can also destabilize the water’s pH levels, which is bad for your betta.
You could use an air stone (aka bubbler) to remedy this problem, but using a filter is easier as it does two jobs.
Keep in mind that if your betta lives in a small tank, stirring up its water can stress it out.
If your betta tank is less than 2.5 gallons, then you could use a low-flow filter. However, we generally recommend putting your betta in a five-gallon tank or more.
Can Betta Survive Without a Filter?
Theoretically, yes, betta fish can survive without a tank. However, this will require extra care on your part, and they’ll still be at risk.
In practice, bettas need a filter to survive because otherwise, they’re prone to suffocating in filthy water or dying of an illness due to contamination.
Here’s a good analogy: imagine you’re staying in a closed room with no windows. It might take a few days or even a couple of weeks, but eventually, you’ll struggle to breathe good air.
Now imagine you also eat and throw your waste in that closed room. Could you live comfortably in that room without an air filter?
The same goes for bettas. Yes, they could survive without a filter, but you’d have to introduce bacteria into the filter to feed on waste and toxins and change their water frequently. Or you could save yourself the hassle and your fish the risk by getting a water filter.
Water Filtration Methods
There are several ways to filter water. But in a betta’s tank, the three most common ways are mechanical, chemical, and biological filtration.
Mechanical filtration is probably the easiest to understand of the three methods. It uses very thin sieves to strain free-floating waste in the water before it decays and harms the betta fish.
Mechanical filters are easily removable filter media that need to be replaced every 2-4 weeks because waste can build up in the sieve. You can tell when a filter needs to be replaced by looking at it or testing it.
And even though these filters can catch incredibly tiny particles, they’re not enough in a betta tank because they can’t eliminate ammonia, nitrates, and nitrites.
Biological Filtration (Beneficial Bacteria)
Biological filtration refers to the helpful bacteria that feed on tiny toxic substances, specifically ammonia and nitrites. The bacteria then transform these substances into compound nitrates, which are much less toxic to betta fish.
This bacteria needs enough oxygen and a tank temperature of at least 55°F to thrive, ideally higher. But if you’re caring for your betta properly, these water parameters should already be there.
They also need a surface to grow on, such as plants, rock, or sponge. You’ll generally find them in gravel or sponge filter media, but they can exist in others.
And since biological filtration can’t eliminate materials like dust and debris, you shouldn’t rely on it as your sole filter media. Instead, you can use it in tandem with another method.
Although chemical filtration isn’t as common as the two other methods, it has its benefits.
Chemical filtration works by attracting dissolved waste particles, which stick to the filter media.
The most common media used is activated charcoal, but you’ll also find activated carbon and resins. Activated carbon and resins can also boost the nitrogen cycle in your tank by removing pollutants from the bacteria’s food.
The waste particles don’t exactly “stick” to the filter media at the microscopic level. Instead, the media have tiny pores where they store waste. As such, these filters will have to be replaced now and then.
Fun Fact: Filtration alone is effective in cleansing aquatic water. What about air pumping? Read about this topic, “Do Betta Fish Need Air Pump? We Take A Breather On This!” for more details!
Types of Filters
Before buying a filtration unit, you should be familiar with the different filter media for betta fish:
Power filters are the most popular filter type in fish tanks, partly because they’re easy to install and maintain. They’re also called hang-on-back (HOB) filters because they hang off the back of a bettas tank and siphon the water out.
These filters use the three filtration methods simultaneously for efficient filtration. They achieve mechanical filtration by flowing the water through a filter paper. There’s also an activated carbon piece on the water’s path for chemical filtration. Lastly, the bacteria on the filter cartridge provide biological filtration.
Sponge filters are internal filters wrapped around or placed over an air pump, where the water output creates a habitat for helpful bacteria to grow and provide biological filtration.
Sponge filters also use mechanical filtration, but it’s relatively faint compared to power filters. However, this makes sponge filters an excellent option for calm betta fish tanks, such as breeding and quarantine tanks.
The lack of chemical filtration in most sponge filters means that medication will stay in the water for longer, which is ideal in quarantine and hospital tanks. Since mechanical filters aren’t very powerful, sponge filters are suitable for breeding tanks that contain tiny betta eggs and fry.
Canister filters use powerful mechanical filtration in canisters best-suited for larger tanks. We’re talking 30 to 40+ gallons here, so a canister filter would be overkill if your tank is smaller.
The canisters are placed externally and connected to the tank through siphon tubes. They’re typically placed behind or underneath the tanks, so they’re pretty subtle.
The large canisters use mechanical, chemical, and biological filtration very efficiently, making them suitable for larger tanks. But this also means they’re much more expensive than your average two betta fish tank.
Under Gravel Filters
One of the most subtle filter types, under gravel (UG) filters, use a wide plate under the tank’s substrate. This plate is connected to an air pump that pulls the tank water down, removing the contaminant particles through gravel. The main advantages of UG filters are that they’re cheap, practically maintenance-free, and easy to set up.
However, they only use mechanical filtration, so you’ll have to install the other two methods separately.
How to Pick a Filter for Bettas (And Other Tropical Fish)
Ideally, your tank needs to simultaneously have all three filtration techniques: mechanical, biological, and chemical. However, it’s not a deal-breaker if your filter doesn’t have them since you can install them separately.
The filter shouldn’t stir the water too much since doing that can aggravate the bettas. For your convenience, you might want to opt for an easy-to-maintain filter where you can replace the media easily.
Fun Fact: Cloudy water is one issue that gives rise to fish problems like diseases and stress. It is better to know what causes this rather than focus on the remedy only. Read our article about Betta Fish Cloudy Water: Causes And Treatment Of Dirty Aqua for a more detailed explanation.
Frequently Asked Questions
Can a betta fish live without a filter for a day?
This depends on the water condition. If you regularly filter the water but decide to remove it for one day, this isn’t harmful, especially since betta fish breathe air if their water is dirty.
However, if the water is contaminated and cloudy, your betta fish won’t necessarily die, but it can get agitated or uncomfortable. For more on this, learn more about how often you should change the aquarium filter.
Do betta fish need a bubbler?
No, betta fish don’t strictly need a tank bubbler because their labyrinth organ allows them to breathe atmospheric air directly. That being said, your betta might enjoy a bubbler in the fish tank.
Do betta fish need a filter? To understand this question, you need to know what filters do and what happens to the water without them.
Over time, if you leave a betta tank to its devices, it’ll accumulate harmful waste. In the wild, wastes are filtered by helpful bacteria, and natural water changes through droughts and rainstorms.
So no, betta fish can live without an internal filter if you ensure their water is clean and oxygenated through regular aeration and frequent water changes. But even then, there’s a risk, and it’s much easier for you and safer for the betta if you use a filtered tank.