Is a 20 gallon tank ideal for betta fish?

In this blog we will discuss bettas in a 20 gallons tank.This comprehensive guide will give all the necessary information regarding the right tank size for bettas.This will help new betta enthusiasts about what should be included in a 20 gallons betta tank.


In this blog

  • Is a 20 gallon tank ideal for betta fish?
  • What is the ideal water parameter for betta fish in a 20 gallons tank?
  • Is it possible to house tank mates with betta fish in a 20 gallon tank?
  • How frequently should you replace water in a 20 gallon betta tank?
  • How long can a betta live without changing the water in a 20 gallon tank?
  • Substrate requirement for a 20 gallons tank
  • Can you add live plants in a 20 gallons betta tank?
  • Heaters for 20 gallons betta tank
  • Filters for 20 gallon betta tank
  • Water conditioner for 20 gallons bettas tank
  • How many female bettas can be accommodated in a 20 gallon tank?
  • How many male bettas can be kept in a 20-gallon tank?
  • Best 20 gallons betta tanks
  • Summary 
  • Frequently asked questions
  • Reference 

Is a 20 gallon tank ideal for betta fish?

A betta ideal size tank is 5 gallons or more for a single male or female betta.  If you plan to keep a lot of community fish, the aquarium needs 1 gallon of water for every inch of fully grown fish.

If you accommodate bettas in a tank that is very small, they will not grow to their full size. However, even the largest tanks should never exceed 3 inches in size.

Tank sizes under 20 gallons are usually a problem.Sizes over 20 gallons provide enough territorial space to accommodate multiple males. However, few people keep bettas in such large aquariums.

The tank should never be too big for your bettas and make sure the bigger tank is planted and not too deep.

What is the ideal water parameter for betta fish in a 20 gallons tank?

Bettas prefers mild water with a pH of 6.8-7.5. They may appear to tolerate lower temperatures,but they become sluggish and susceptible to illness, so keeping the temperature between 76-85F for their overall health is better.

Bettas prefers soft water, but withstands a wide range of GH from 5 to 20 DH or 70 to 300 ppm. Very hard water can be harmful to them. Mixing Indian-almond leaves, alder cones, RO or distilled water reduces the hardness of the water.

Is it possible to house tank mates with betta fish in a 20 gallon tank? 

If you are interested and planning on getting a tank companion for betta fish, then a 20 gallon tank is the best size.

This size can accommodate fish such as Tetra, which require extra space to swim, and fish that may grow slightly larger than bettas  such as Molly.

  • Malaysian trumpet snails.
  • Ember tetras.
  • Harlequin rasboras.
  • Cory catfish.
  • Kuhli loaches

How frequently should you replace water in a 20 gallon betta tank?

  • For the best health of the bettas, it is best to change 10-20% of the water every 7-10 days. This also assumes that you are using a filter. 
  • 20-30% water changes can be done once every 2-3 weeks, but for a stable water condition, it is better to do changes less frequently.
  • If you don’t have an aquarium filter, it is recommended that you replace 30% to 50% of the water.
  • You can reduce the frequency of large water changes, i.e. 20 to 30 percent every 2 to 3 weeks, but small water changes will help your betta get more balanced water conditions. 

How long can a betta live without changing the water in a 20 gallon tank?

With the right equipment and well-equipped tanks with the right power filters, good quality and well-planned feeding schedules will ensure that bettas can go for about a week without changing water in their tanks.

But, to be honest it is very important to do water changes to remove leftover bioload and built up toxins in their tanks.One should not take it lightly when it comes to routine water changes in bettas tanks.

Substrate requirement for a 20 gallons tank

Always prefer gravel to sand when choosing a substrate for a bettas tank and If you don’t know the amount of gravel, use 1 pound per gallon in the tank as a rule of thumb.

And remember that changes when the tank isn’t a standard rectangle. Don’t forget to use only good quality gravel that is neither too small nor too big.

Can you add live plants in a 20 gallons betta tank?

Yes you can definitely add live plants in bettas tank,because bettas come from areas with lush green vegetation and they need lots of hiding spots too in their tank.

Live plants will play a dual role by purifying the tank environment and providing covers too for hiding.

  • Java fern.
  • Amazon sword plant.
  • Hygrophila.
  • Hornwort.
  • Marimo moss balls.
  • Anacharis.

Heaters for 20 gallons betta tank

An aquarium heater can help you maintain the correct water temperature for your aquatic friend. The most important thing to consider when choosing one is its ability to easily read the current temperature and heat it up.

Therefore, the choice of a heater with an understandable temperature is always critical.You can choose from the below mentioned tank heaters suitable for your 20 gallon betta tank.

  • SZELAM smart mini aquarium heater (25 Watt)
  • Eheim jager aquarium thermostat heater (25 Watt)
  • Hydor slim heater for bettas (7.5 – 15 Watt)
  • Hygger submersible mini aquarium heater (50 Watt)
  • Aqueon aquarium heater (50 Watt)
  • FREESEA aquarium heater (25 Watt)
  • ZEETOON betta fish tank heater (25 Watt)
  • Cobalt aquatics flat neo-therm heater (25 Watt)
  • Fluval M50 submersible heater (50 Watt)
  • Hygger titanium aquarium heater (50 Watt)

Filters for 20 gallon betta tank

Betta fish require clean water to survive in their tank just like any other fish. Poor water conditions can cause your betta fish to become ill or have problems such as fin damage.

Filters are very helpful in preventing the buildup of harmful microorganisms and organic detritus from leftover food and fish excrement. 

Passing the water in the tank through a filter also helps to oxygenate the water. This may improve the overall health of the bettas. Betta fish work well with low flow filters.

Else, it tends to be knocked down by the current generated by the high power filter and can cause stress.It is very important to choose their filters wisely,as it can affect their swimming patterns completely.

List of aquarium filters for betta fish:

  • Fluval 206- External canister filter
  • Xinyou XY-2831-Sponge filter
  • AquaClear power filter-HOB (Hang on Back) filter
  • Lee’s 40/55 premium undergravel filter
  • Jardin aquarium Corner filter
  • Koller products TOM- Internal power filter

Water conditioner for 20 gallon bettas tank

The ideal pH for bettas is 7 or slightly more acidic. SeachemPrime is the best water conditioner for solid fish because it detoxifies ammonia, nitrites and nitrates and dechlorinates water.

Making tap water safe for bettas is incredibly easy, you just need to add a water regulator in advance.

Water conditioners process water very quickly, but it is advisable to leave the water in the tank for 1-2 days before adding solids. 

How many female bettas can be accommodated in a 20 gallon tank? 

Female bettas are much better than male bettas and can live with other female bettas and even other fish species too in community tanks and you should keep at least five female betta in the sorority, in a 20 gallons or 75 liters of water. 

For bettas, bigger is always better, because the larger the aquarium, the more stable the water parameters.

How many male bettas can be kept in a 20-gallon tank?

The size of more than 20 gallons provides sufficient space to hold multiple males.

Some people house bettas in larger tanks but traditionally bettas are kept in very small tanks, hence the general expression of one male betta per tank should be the rule of thumb.A more precise way would be putting one male per 20-gallon territory.

Best 20 gallons betta tanks

20 gallons seaclear acrylic combo set

The main reason you should buy this tank is that it is acrylic. Acrylic tanks reduce temperature fluctuations, are stronger than glass and allow you to see the fish more clearly. 

It also comes with LED lights so you don’t have to worry about buying. The biggest drawback with this tank is you have to buy more things such as heaters and filters and the top is only partially covered. Therefore, cleaning can be more difficult than with a regular tank.

20 gallons ecolife aquaponic garden system tank

  • The concept is great, not only can you keep the betta fish, but you can also grow your own food. 
  • Stunning LED lights and many different programs you can run.
  • This is a great educational tool for anyone who wants to understand the relationship between plants and animals. 
  • You don’t have to clean the tank as often as the plants will do the needful.
  • If aquaponics isn’t your thing, this aquarium has a lot of useless features. 
  • Because it has more moving parts, it may be more difficult to maintain after a regular aquarium.


  • If you’re interested in finding a tank buddy for your betta, a 20-gallon tank is a great option.
  • A 20-gallon aquarium will be a great option for housing tank mates with bettas. 
  • Make sure not to overcrowd the tanks by adding too many tank mates,as it can stress bettas and other tank mates too.
  • Provide lots of covers and swimming space to make them feel safe and secure.
  • Avoid frequent water changes in bettas tanks,as it is stressful for them.
  • Leftovers or uneaten food should be removed daily using a gravel siphon to avoid ammonia buildup in their tanks.
  • Avoid keeping male bettas together and avoid keeping them with other species too.
  • Male and female bettas should be kept only for breeding purposes,and females should be removed immediately after they lay their eggs.
  • Choose tank mates wisely as finnippers and brightly colorful companions can stress them.
  • Always keep female bettas in a group of 3 together.
  • Always quarantine new tank mates for 2 weeks before adding to the 20 gallons tank.
  • Heaters,thermometer and filters are very important in bettas tanks.

Frequently asked questions

Is it possible to keep two betta fish in a 20 gallon tank? 

Yes, you can combine two or more betta fish, but you have to follow some rules,do not put two male bettas together, because they will fight until one dies.

How many bettas can be accommodated in a 20 gallons tank?

You can keep 1 male betta  or  1-3 female bettas in a 20 gallon tank.