Do Betta Fish Need a Filter?

by Kevin

Do betta fish need a filter

Betta fish are often sold without an aquarium filter because they are able to live in smaller tanks or bowls.

The reason betta fish can survive in small bowls is thanks to their labyrinth organ, which allows them to breath atmospheric air.

In a betta’s natural environment, which includes rice paddies, small pools, and ponds, this ability to breath air is a huge advantage.

In the wild, betta fish are able to survive drought and low water conditions until the next rainstorm occurs.

But, in captivity, betta fish rely people to change the water.

And if that water is not changed regularly, especially if the betta is living in a small bowl or vase, then bacteria and fungus will eventually kill the fish.

So, betta fish can live without a filter, but having using a filter for your betta, like a sponge filter, will help maintain healthier water conditions and disaster.

The most ideal environment for a betta fish in captivity is a planted tank of 3+ gallons with a filter and heater.

How Do Aquarium Filters Work?

Aquarium filter illustration

Filters can provide 3 different types of filtration:

1) Biological

Biological filtration is conducted by bacteria and other microorganisms, which process and convert fish waste into less toxic compounds.

Ammonia is converted into Nitrates, which are eventually converted into Nitrites.

Without biological filtration, the only way to ensure livable water conditions, is to provide constant water changes, sometimes twice a day (depending on the size of the tank and the bio load).

Biological filtration kicks in when your tank is “cycled.”

A cycled tank refers to an aquarium that has been left to sit for 2-4 weeks, which allows nitrifying bacteria to colonize in the tank.

The physical spaces and surfaces within aquarium filters provide an excellent place for nitrifying bacteria to colonize.

Aquarists will often add “filter media” inside the filter to encourage bacterial growth.

2) Mechanical

Mechanical filtration is achieved by pushing water through “filter media,” which acts as a strainer.

Larger, free-floating particles are caught in the filter media, which can then be cleaned by the aquarist.

Filter media types include: filter floss, commercial filter pads, sponges, and gravel (under gravel filters).

The size and density of the filter media will affect the clarity of your aquarium water.

For example, a sponge with large holes will filter large particles, while a sponge with minute holes will filter out almost all debris.

However, denser sponges also clog faster and must be cleaned more often.

Mechanical filtration almost always goes hand-in-hand with biological filtration because bacteria will colonize inside the surfaces of the filter.

3) Chemical

Chemical filtration involves the addition of carbon or chemical resins to a filter for the purpose of removing specific toxins or medications from the water.

Activated carbon is a common addition to filters, and effectively removes a number of metals and chemical from the water.

Activated carbon eventually becomes saturated, so it must be changed periodically (at least once every 60 days) to remain effective.

Activated carbon does not remove ammonia, nitrates, or nitrites, and therefore cannot replace biological filtration.

Having a cycled tank that is still essential to optimal fish health.

Can betta fish survive without a filter?


But think about it . A betta in a bowl is like a guy in his car who cannot roll down his windows.

Eventually the air gets really stale in the car, especially if car exhaust is leaking in.

Without a filter, ammonia builds up quickly in small bowls or tanks and additional water changes need to be performed as compared to a tank with a cycled sponge filer.

Aquarium filters circulate water and provide a home for nitrifying bacteria to colonize in the filter media.

These bacteria break down toxic ammonia and reduce the need for constant water changes.

A betta fish tank with a filter is far more ideal than one without a filter.

But, be cautious about buying just any filter.

The long, flowing fins of a betta fish are not suited to strong currents.

If your betta is constantly battling a current, he may become weak, and even die.

Filters Found in Aquarium Kits

Power filters, or hang-on-back filters are perhaps the most common filters provided in aquarium kits.

And beginner aquarists often buy aquarium kits.

Power filters are actually great for a variety of fish and tank setups, but power filters are often harmful to betta fish.

Many power filters simply provide too much current, especially if your betta is housed in a tank under 10 gallons.

The Best Betta Filter

The best betta filter is one that does not push your betta around the tank like a balloon.

The output of aquarium filters varies in strength, but are often too strong for a betta fish because these filters are designed to rapidly push water from one end of the tank to another.

If your betta appears to be hiding from the current, or swimming frantically against the current, the filter flow is too strong.

This can be remedied immediately by purchasing a sponge filter for your betta tank, which also makes a great filter for shrimp as well.

Alternatively, you can reduce the output of your filter by placing an aquarium sponge over the intake part of the filter.

This should reduce the amount of water that the filter draws in and puts out.

How Do Sponge Filters Work?

Sponge filters may look like just an air stone placed inside a sponge, but physics has turned these filters into impressive waste management systems.

The air bubbles sent down the air tube at the center of the sponge filter must rise again.

As these bubbles rise, they cause water to be drawn through the sponge.

So, if more air is pumped into the sponge, then more water is drawn through the sponge.

Sponge filters provide extremely low flow filter systems that are ideal for bettas, shrimp, and other current averse species.

The sponge on a sponge filter is a mechanical filtrations system but also provides a large surface area for nitrifying bacteria to colonize.

The downsides of sponge filters are that they need to be cleaned. Debris and detritus will become stuff to the filter and, over time, will inhibit water flow.

Sponge filters are also not especially visually pleasing.

But, careful placement of rocks and large plants can remedy that.

Overall, sponge filters make excellent filters for any betta tank.

Basic Betta Tank Setup

Ideal Betta Tank Setup

1) 5-10 gallon tank

2) Sponge filter

3) Heater

4) Live plants

Decent Betta Tank Setup

1) 2.5-5 gallon

2) Sponge filter

3) Heater

4) Live or silk plants

Betta Tank Setups to Avoid

1) Under 2 gallons

2) No filter

3) No heater

4) No décor or decorations with sharp edges


Keeping a betta without a filter is certainly possible.

But, keeping your betta with a filter is actually easier.

Filters provide:

1) A home for beneficial nitrifying bacteria – waste and ammonia reduction.

2) Oxygen – Filters circulate water and oxygenate the water.

3) Possibility for tank mates – a filter helps deal with the additional waste and bio load that other fish produce.

4) Stable water chemistry – fewer water changes and maintenance.

Without a filter, maintaining the nitrogen cycle and keeping a healthy tank become much more difficult.

A betta fish’s lifespan tends to be short and their health poor when kept in a tank without a filter.

Just be sure to choose a low flow filter for your betta, or modify an existing filter to reduce water output.

Also, while filters provide reduced maintenance, that does not mean water changes are eliminated.

Continuing to perform at least 20% water changes weekly will help create optimal conditions for your betta fish.

Stay zen aquarists.