Betta Macrostoma (Spotfin Betta or Brunei Beauty) Care Guide

Last Updated: February 20, 2023 by Dave Gibbins

Betta macrostoma (macrostoma betta), also known as the spotfin betta or the Brunei beauty, is quite different than many other popular betta varieties.

They, unfortunately, find themselves on the IUCN Red List of Threatened Species, on which it is listed as Vulnerable, mainly due to their habitat being constantly taken away. These bettas can be difficult to find in captivity but are a fascinating fish to learn about. If you are keeping one as a pet please do your research to help ensure that it lives a long, healthy life.

Quick Facts Table

Size: Three and a half to four and a half inches

Lifespan: Three to 10 years

Ease of care: Expert

Native to: Shallow ponds or rivers in Borneo

Minimum Tank Size: 20 gallons for a pair, 40 for a group

Water type: Clean freshwater with a stable pH and temperature

Temperature: 70 to 80 degrees Fahrenheit

Compatibility: Not compatible with other tankmates

Diet: Frozen or freeze-dried meaty foods or commercial pellets

Overview

One of the rarest and most expensive betta varieties available, the betta macrostoma is quite different in both appearance and personality than many of the more popular betta varieties, such as betta splendens.

Betta macrostoma are somewhat less flashy in appearance than other captive-bred betta varieties. In addition, they don’t build bubble nests but are instead mouthbrooders, so their faces are somewhat wider than other bettas’.

Betta macrostoma are also a bit more peaceful than their betta cousins. Although males can still become territorial, these fish are best kept in pairs (or groups in larger aquariums). However, they should be kept only with their own species as they can become too territorial with other tankmates.

Due to habitat loss, wild betta macrostoma are threatened, so most pet macrostoma are raised in captivity. Because the species is so rare, and because these fish can be somewhat temperamental when it comes to water chemistry changes, it’s generally recommended that only advanced aquarists keep this species.

Betta Macrostoma Appearance

When considering what type of betta to choose, you may wonder, “What do betta macrostoma look like?” or “How big are betta macrostoma?” The spotfin betta is quite large, reaching between three and a half and four and a half inches in length. They have short, round fins, wide mouths, and red, brown, white, and black coloring. Males are more colorful than females.

They have such a lovely appearance. They don’t get the name Brunei beauty for nothing!

Betta Macrostoma Lifespan

Like other betta varieties, betta macrostoma generally live for between three and five years. However, some people have reported that these fish can live much longer, averaging between eight and 10 years.

Habitat and Tank Size Requirements

Betta macrostoma do best when kept in larger aquariums. A 20 gallon aquarium is suitable for a pair, while groups should be housed in an aquarium of at least 40 gallons.

These fish are excellent jumpers, so a tight lid with no gaps is essential. 

These bettas will do well in a planted tank with plenty of hiding spaces. A bare bottom is often a good choice, particularly for breeding pairs. Aquarium leaf litter can add a more natural look and will also aid in maintaining steady, healthy water conditions.

Betta macrostoma aren’t picky when it comes to water conditions. They can tolerate a wide variety of pH levels, although a pH over 6.0 is recommended. The water temperature should be between 70 and 80 degrees Fahrenheit, with a cooler temperature being preferable, unlike the warmer temperature needed for B.smaragdina.

Betta Macrostoma Care

The most important thing to remember with these particular fish is that they do not react well to water chemistry changes or temperature changes. Any sort of fluctuation can cause health problems, so it’s crucial to keep the water clean while also ensuring that the chemistry and temperature remain stable.

Partial water changes, where only about 10 to 25 percent of the water is changed, performed about every two weeks, can help to keep the water clean without changing the chemistry. Sponge filters can also encourage the growth of beneficial bacteria without creating too much water current.

Remember that, before adding any betta macrostoma to your tank, the aquarium should be fully cycled so that there are no harmful nitrites, nitrates, or ammonia present.

Feeding

Betta macrostoma are omnivorous. They can be fed various foods, such as commercial betta pellets, frozen or freeze-dried bloodworms, or brine shrimp, to get all the vitamins and nutrients they need.

Like other betta species, macrostoma should be fed once or twice a day, and they should only be offered as much food as they can eat in a few minutes.

Breeding

When kept in pairs, these fish will breed naturally. During spawning, the male will wrap around the female many times. As the female lays the eggs, the male will fertilize them. This spawning behavior can last for between two and five hours.

After the spawning is complete, the male and female will both collect the eggs from the floor of the aquarium. The female will pass the eggs to the male, and the male will hold them in his mouth until they hatch. Incubation usually takes between 30 and 35 days, although some sources quote a much shorter incubation time of between 12 and 17 days.

While the male is mouthbrooding, the fish should not be disturbed in any way. The female should be left in the tank, and the male should not be fed. Disturbing or feeding the male can cause him to swallow the eggs. After two weeks, the female can be removed. Once the fry hatch, the male can also be removed.

Generally, between 10 and 20 betta macrostoma fry will hatch, and only about 15 percent will be males.

Price

Because they are so rare, finding a macrostoma betta for sale can be a challenge. When they are offered, these fish generally cost about $50. They are less expensive than unsexed juveniles. Breeding pairs can also be purchased, but they generally cost about $200.

Choosing the Best Betta Macrostoma

When purchasing betta macrostoma, it’s best to buy from a reputable breeder who has captive-bred fish. The breeder should be able to tell you exactly how old the fish are and what type of water conditions they have been raised in.

Choose fish that appear healthy, with no discolorations or torn fins. In addition, fish should be active and have strong appetites. Lethargy or loss of appetite can be signs of illness.

Overall, betta macrostoma can be a beautiful, interesting pet, but because the breed is so rare, they’re best kept by people with a good amount of betta and fishkeeping experience. In addition, people who keep these fish are encouraged to breed them in order to support the species, and when kept in pairs, they’ll breed readily. For this reason, be prepared to raise and house any fry.

Betta macrostoma also require a large amount of space compared to other betta species, and their water chemistry and temperature must be kept very stable.

Have you kept betta macrostoma, or do you have a question about this species? Let us know by commenting below.