Betta Macrostoma Care Guide: Tank Setup, Size & Breeding


Common Name(s)Spotfin Betta, Brunei Beauty
Scientific NameBetta Macrostoma
OriginMalaysia
Temperature75-79°F (24-26°C)
Size3.5 inches
Minimum Tank Size20 gallons
Food & DietOmnivores that prefer a high protein diet
Lifespan3-5 years
Water pH6.0-7.0
Tank MatesA single specie tank is recommended
BreedingMouth brooders that breed in pairs. Breeds without a bubble nest.
DiseaseMay be suseptible to fungal infection, fin rot, and gill flukes.
Betta Macrostoma
Betta macrostoma fry. John Pittman, CC BY-NC-SA 2.0.

Betta Macrostoma, also known as the Spotfin Betta or the Brunei Beauty, is one of the rarest betta fish in the fish-keeping realm. The betta fish requires specialized care to maintain and enhance overall well-being. This guide will provide you with expert information and instructions regarding optimal environment, proper nutrition, and successful breeding.

The Betta Macrostoma is a beautiful, bright orange-colored fish with a small dorsal fin that displays a black and orange eye-like spot, hence its alternative name, the Spotfin Betta. The caudal fin has black stripes and orange patches, while the other fins are dark orange with a black edge. Its main distinguishing feature is the large mouth, as its Latin name signifies (“macro” meaning large and “stoma” meaning mouth).

The Betta Macrostoma is native to Brunei and to northern Sarawak in Malaysia. Agricultural development caused its natural habitat to be rapidly destroyed, leading to a steep decline in the population. In Brunei, it was believed that this betta fish had gone extinct; fortunately, in the 1980’s, the betta fish was found in certain areas of the region. Today, it remains listed as an endangered and vulnerable species. It is protected by law in Brunei; consequently, it is illegal to catch or possess wild Betta Macrostoma. Most Betta Macrostoma available for fish-keepers either originate out of Malaysia or have been bred in captivity. The enthusiastic interest for maintaining and breeding Betta Macrostoma allows for the wild population to thrive. Thus, while it is a careful task to care for these beautiful creatures, it certainly has far-reaching positive effects beyond the individual aquarium.

Betta Macrostoma Care

The most significant part of Betta Macrostoma care is to create an optimal environment. The following sections will discuss how to recreate the bettas natural environment with specific instructions regarding aquarium parameters.

Tank Specifications

The Betta Macrostoma requires a minimum tank size of 20 gallons per pair.  If housing a small group or school of Betta Macrostoma is preferred, the recommended minimum tank size is 50 gallons. It is a very active fish, demanding plenty of space to swim. Moreover, the perfect aquarium size allows for a betta fish to reach its full growth potential and lifespan; the betta macrostoma can grow up to 4.5 inches long although the average size is 3.5 inches. The average Betta Macrostoma lives three to five years in captivity. However, with an optimal environment, fish-keepers have reported a ten year lifespan possibility.

It is important that the aquarium has a tight-fitting top, as betta fish have an extraordinary skill to jump out of the water. Although the chance of jumping decreases with appropriate water conditions, the only way to ensure the fish remains in its aquatic environment is to have a secure, full-coverage tank lid.

Water Parameters

An ideal aquatic environment for the Betta Macrostoma includes a temperature range of 75-79°F (24-26°C), a pH of 6-7, and a water hardness of 1-10 DKH.

The average tap water pH is much higher than the pH required for the Betta Macrostoma; it is important that the pH does not go above 7 and is maintained consistently with little variance. There are many ways to reduce pH and maintain that level, reflecting natural conditions. The first method is to provide driftwood, which will release tannic acid over time, effectively lowering the pH. Driftwood also provides natural shelter for the betta fish. An additional excellent way to lower pH is to introduce peat moss or almond leaves to the aquarium.

The Betta Macrostoma is sensitive to nitrates and ammonia, and it disfavors drastic changes in water chemistry. Therefore, it is best to strike a perfect balance between cleanliness and the specific water parameters. There are three fundamental ways to achieve such a task: living plants, sponge filter, and partial water changes.

  1. Introduce living plants to the aquarium! Living plants will improve the water quality; they will absorb ammonia and nitrates, and they will oxygenate the water.
  2. Choose a sponge filter. A sponge filter is ideal because it allows for beneficial bacteria to grow while providing slow-flow filtration. This closely mimics the natural environment of slow-flowing streams and rivers.
  3. Do partial water changes every week. An excellent way to maintain clean conditions in the aquarium without disrupting the water chemistry drastically is to carry out 25% water changes every week.

Betta Macrostoma Tank Setup

In the wild, the Betta Macrostoma lives in shallow, low-current pools found in freshwater streams and rivers. The surrounding area is dense jungle, generating an aquatic habitat that is rich in vegetation, organic decomposition, with a substantial amount of branches and plant matter used as refuge and shelter. An ideal aquarium set-up would attempt to imitate this environment.

The recommended lighting arrangement for the Betta Macrostoma is low or dim lighting. In the Brunei and Sarawak regions, thick rainforest creates a natural canopy overhead; the water itself is also filled with vegetation, which provides further coverage from sunlight. If the aquarium lighting is too bright and direct, the betta fish will become stressed. In order to create a peaceful environment, provide low lighting, floating plants, and many pieces of driftwood or clay pottery for places to seek refuge or shelter. A further option to dim any sunlight coming through the sides of the aquarium would be to purchase an aquarium with shaded glass or to apply a dark background to three sides of the tank.

There are many plants that are appropriate for the Betta Macrostoma; appropriately selected plants flourish in freshwater, dim lighting or shady environments, high acidity or low pH, and a 70-80F water temperature. Some of the most popular plants for this fish include:

  • Java fern is one of the easiest types of plants to care for. They do not have roots and will attach to rocks or driftwood. They have long green leaves, providing places for the betta to hide. 
  • Java moss provides a comfortable, thick mat, allowing for your betta fish to rest within its tufts.
  • Anubias has hardy, teardrop shaped leaves upon which the betta fish can rest.
  • Frogbit and water sprite are excellent floating plants that produce roots growing downwards into the water. These provide shade from light and many hiding places.

The Betta Macrostoma does not require substrate, and many fish-keepers choose to take advantage of this in order to make cleaning their fish tanks easier. That said, medium-sized or large-sized gravel would also be appropriate.

Betta Macrostoma Food & Diet

Betta Macrostoma are omnivores that prefer a high protein diet.

Most Betta Macrostoma will not eat dry flake or pellet food, even if they are captive bred. Therefore, it will be neccessary to feed live fish food, fresh food, or frozen food. Types of food that they will eat include shrimps, black worms, bloodworms, glass worms, white worms, mosquito larvae, brine shrimp, and crill.

Dry flake food and pellet food is convenient and can provide a nutritionally balanced source of food. However, Betta Macrostoma may not accept the dry food.

Betta Macrostoma Tank Mates

The Betta Macrostoma is peaceful in terms of behavior, especially compared to the betta splendens which is regarded as aggressive and territorial. The male Betta Macrostoma can be aggressive towards another male. However, in a suitably sized aquarium, the territorial fights should be inconsequential and infrequent.

Although the Betta Macrostoma is peaceful, it is incompatible with other fish species. If they are placed with other smaller fish, they might attack it and try to eat it. If they are placed with larger fish, Betta Macrostoma will become agitated or stressed. It is best to only pair the Betta Macrostoma with its own kind; a male and female will do exceptionally well as long as they have paired organically prior to being placed alone.

Betta macrostoma breeding pair. John Pittman, CC BY-NC-SA 2.0.

Betta Macrostoma Breeding

A successful breeding process for the Betta Macrostoma involves a naturally chosen pairing of a male and female betta fish, a peaceful spawning and brooding period, and care for fish fry.

A tank set-up for Betta Macrostoma breeding does not require a drastic change from an original, ideal tank set-up. The best environment will be dimly lit, and filled with living plants and driftwood. This will help the betta fish feel comfortable, increasing the chances of having a successful breeding period. Additionally, it is excellent to have a slow-flow filter and no substrate because this allows the fish fry to remain safe. Some breeders indicate that a breeding tank should have a slightly higher temperature than normal to mimic “breeding season” in the wild, which is in late winter and spring, and that the pH should remain below 6.

It is easy to distinguish the Betta Macrostoma male from the female. The male fish is bright orange or reddish while the female fish is a more dark and muted brown color with two black bands running along its sides. The male and the female fish must find their pairing naturally, prior to being placed together in an aquarium; only then will they be able to cohabitate peacefully. This can be accomplished by grouping one male with a pair of females, and patiently waiting for the male to choose a female; alternatively, many fish-keepers who have schools or groups of Betta Macrostoma notice these pairings occur without isolating one male with a group of females.

Once the male and the female have paired successfully, the female will start the breeding process by performing a betta fish dance in front of the male; this showcase involves flaring and fin flapping. The male will respond in kind and it will also open its mouth wide. The female will mirror this behaviour. Subsequently, the male will wrap around the female in an embrace until his pelvic fin rests on the female’s mouth; this will stimulate the female to release her eggs and the male will fertilize them.

Unlike the Betta Splendens, who builds a bubble nest and allows the eggs to hatch, the Betta Macrostoma is a mouth brooder. A mouth brooder will pick up the eggs in his mouth; the female will help by picking up the eggs and spitting them into the males mouth (this is often compared to a “kiss” action).

Once he has successfully gathered the eggs, he will incubate the eggs for up to a month. He will refrain from eating, and he will spend most of his time resting. It is important that the incubation period is as peaceful as the breeding and spawning process; if the male becomes stressed, he can swallow the eggs. It is suggested to remove the female betta from the aquarium such that the male does not become threatened by her presence.

Further, during this time, it is just as, if not more, important to keep the water quality stable; it is recommended to only do small, partial water changes and to avoid introducing anything new to the aquarium environment.

After 30-35 days, the Betta Macrostoma fry will be released. They will range from 0.2 to 0.3 inches in length. Since the fish fry are tiny, they are susceptible to being eaten by their parents. If there is dense plant coverage, the fish fry should remain protected and safe as they would in a natural habitat; however, it is also suitable to remove the parental fish from the aquarium.

Nutrition plays a critical role in the optimal growth and overall health of the fish fry. A healthy diet for the Betta Macrostoma fry would include small larvae, worms, and shrimp; nutritious options include baby brine shrimp, daphnia (water fleas), fairy shrimp, microworms, and vinegar eels.

Fry are more sensitive to water changes than adult Betta Macrostoma; it is important to monitor the water quality and temperature frequently. Fish fry also release a Growth Inhibiting Hormone into the water, which can hinder and halt the growth of other fish fry if the hormone builds up. Since this is the case, it is suggested to complete a 10% daily water change.

Fry will grow fairly rapidly; at around two months of age, their colors become more prominent and defining, allowing clear male and female identification. At this point, the male fish fry will become more aggressive towards each other. This is a good time to move the betta fish into their own aquariums or into small groups.

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