Betta Macrostoma Care Guide: Tank Setup, Size & Breeding


Common Name(s)Spotfin Betta, Brunei Beauty
Scientific NameBetta Macrostoma
OriginMalaysia, Brunei
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 species tank is recommended
BreedingMouth brooders that breed in pairs. Breeds without a bubble nest.
DiseaseMay be susceptible 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, is one of the rarest wild Betta fish in the fishkeeping hobby. They are beautiful fish with bright orange-coloration. They have a small dorsal fin that displays a black and orange eye-like spot, which is why they are called 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).

Betta Macrostoma are native to Brunei and northern Sarawak in Malaysia. However, agricultural development have caused destruction of many of its natural habitats, leading to a steep decline in the wild population. In Brunei, it was once believed that this betta fish had gone extinct. Fortunately, in the 1980’s, Betta Macrostoma were discovered again in certain areas of the region. Today, it remains listed as an endangered and vulnerable species. In fact, it is protected by law in Brunei and it is illegal to catch or possess wild Betta Macrostoma. Therefore, most Betta Macrostoma available for fishkeepers originate out of Malaysia or have been bred in captivity. Hobbyist who breed these fish in captivity or purchase captive-bred specimen would help reduce the pressure on the wild population.

These fish require specialized care for in order to thrive in an aquarium. This guide will help you understand how to properly care for this rare and special fish.

Betta Macrostoma Care

Taking care of Betta Macrostoma starts with a proper tank setup. In order for these fish to thrive, an aquarium that mimics their natural environment should be set up. This would entail a proper aquarium tank, aquarium heater, aquarium filtration, and water parameters. Proper feeding and regular maintenance is important as well.

Betta Macrostoma require a minimum tank size of 20 gallons per pair. If you wish to keep a small group of these fish, a larger tank of at least 50 gallons is recommended. They are active fish that required plenty of space to swim. Providing adequate space for the fish will allow them to grow to their full size and live as long as they can.

Regarding their size, Betta Macrostoma can live up to 4.5 inches in length. However, the average size for these fish is 3.5 inches.

Regarding their lifespan, Betta Macrostoma can live 3-5 years in captivity on average. However, some specimen are known to live up to 10 years. Optimal environments and good genetics would contribute to a long lifespan.

Water Parameters

Regarding the water parameters for Betta Macrostoma, they prefer a temperature range of 75-79°F (24-26°C), a pH range of 6-7, and a water hardness of 1-10 DKH.

A pH range of 6-7 would be considered more acidic than the average tap water. Since the pH of the tap water would vary based on different regions, it is important to measure it. If the pH is above 7, it must be lowered to match the needs of the fish. There are many ways to reduce the water pH in an aquarium.

Here’s are some ways to reduce the water pH in an aquarium:

In addition to adjusting the pH to the optimum range, it is also important to maintain it. The water pH can change over time, so it should be measured regularly. It is also important to keep the water pH consistent as possible. Even if the pH is within range, it shouldn’t change abruptly.

Betta Macrostoma are sensitive to nitrates and ammonia, and good water quality must be maintained at all times. In order to maintain good water quality, install an aquarium filter, add live aquarium plants, and do regular water changes.

Regarding the aquarium filter, a sponge filter would be ideal. This is because Betta Macrostoma do not like strong water flow. In their natural environment, these fish are often found in slow-flowing or nearly stagnant bodies of water. A sponge filter would be able provide the necessary biological filtration, without the strong currents. The biological filtration will help convert the ammonia and nitrite in to nitrate, which is less harmful to the fish.

Live aquarium plants would be beneficial to the fish, since it will absorb the nitrates in the water. The biological filtration can not remove the nitrates out of the water, but the plants will use as nutrients.

Lastly, regular water changes would help maintain good water quality. While the filtration and live plants will help manage the water quality in between water changes, trace minerals can build up in the tank. Therefore, water changes are vital. When performing water changes, it is important to prevent the water parameters from changing drastically. Therefore, small water changes done on a frequent basis is better than large water change done occasionally. A 10-20% water change on a bi-weekly basis would be ideal. Be sure to monitor the parameters of the water that is being added as well.

Betta Macrostoma Tank Setup

In the wild, the Betta Macrostoma live in shallow, low-current pools found in freshwater streams and rivers. These bodies of water is often surrounded by a dense jungle. Leaves, tree branches, and other organic material would fall into the water, which would explain the low pH of the water. These organic material would provide shelter for the fish as well. An ideal tank setup would mimic these environments.

Betta Macrostoma do not like strong lighting, since the thick rainforest creates a natural canopy in their natural habitat. The submersed vegetation provides additional shade as well. If there is too much light, the fish will become stressed. Direct sunlight or strong aquarium lights should be avoided. Instead, install a dim light and provide plenty of cover. Hardscape such as driftwood and cave structures can be beneficial. Dark colored aquarium background can help as well. Lastly, add plenty of aquarium plants. Floating plants, such as Amazon Frogbit, can help block the light from above very effectively. Plants with large leaves, such Java Fern, can created a shaded area underneath. Aquarium moss, such as Java Moss, can be attached to overhanging driftwood. This can potentially create a large shaded area, especially once the moss is well established. Java Fern and Java Moss are well suited for Betta Macrostoma tanks because they can thrive in low light environments.

There are no special requirements in regards to the aquarium substrate. However, a substrate that does not negatively affect the water quality should be used.

Lastly, add a tight fitting lid to the aquarium tank. Betta Macrostoma are agile fish that are able to jump out of the water.

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, daphnia, and brine shrimp.

If possible, they should be transitioned to a quality dry feed diet. This would make it possible to meet their nutritional needs more effectively. Needless to say, a dry feed diet is much more convenient.

Betta Macrostoma Tank Mates

Tank mates for Betta Macrostoma should be selected with care, and a species only tank is recommended.

A pair of Betta Macrostoma (one male and one female) in a 20-30 gallon tank would be ideal. Since they aren’t particularly aggressive fish, they can be kept in groups as well. While males can show aggressive behavior towards each other, it is possible to keep them in the same tank if it is large enough. There should be enough space to allow each male to establish their own territories. Compared to male Betta Splendens, which are very aggressive, male Betta Macrostoma are less aggressive.

While Betta Macrostoma are relatively peaceful fish, it is recommended to keep them in a species only tank. They have large mouths, and they may eat smaller fish if given the chance. Especially considering how rare Betta Macrostoma are, keeping them with larger fish that may stress or harm the fish should be avoided as well. Even if the fish were compatible in temperament, the specific tank requirements may be different as well. In order to provide the optimal environment for these fish, a species only tank is usually the best option.

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

Breeding Betta Macrostoma

In order to breed Betta Macrostoma, a good breeding pair is necessary. Keep in mind that not all male and female will become a successful breeding pair. The best breeding pairs are established in a group setting, and the females will wait patiently for the male to select them. Once the breeding pair is established naturally, they can be separated into a breeding tank. Naturally established breeding pairs will have a higher chance of spawning peacefully and breeding successfully.

Male and female Betta Macrostoma look very different, so they can be distinguished quite easily. The male are bright orange in color, while the female are darker in color. The female are usually brown in color, with two black bands running along its sides.

A tank setup for a breeding tank would consist of a 20 gallon tank or larger, clean water, and a pH level of 6. The tank should be dimly lit with low water flow. Plenty of hardscape and live plants will create an environment that will help the fish feel safe as well. In addition, a slightly higher temperatures will mimic their “breeding season” in the wild, which is in late winter and spring.

Regarding the spawning process, the female will start by flaring and flapping its fins in front of the male. The male will respond to the female’s “dance” by opening its mouth wide. The female will mirror the male’s behavior by opening its mouth wide as well. Next, the male will wrap around the female in an embrace until its pelvic fin rests on the female’s mouth. This will stimulate the female to release her eggs, and the male will fertilize them immediately.

Unlike the Betta Splendens, who builds a bubble nest and allows the eggs to hatch, Betta Macrostoma is a mouth brooder. The male Betta Macrostoma will pick up the eggs in his mouth, and the female will help by picking up the eggs and spitting them into the male’s mouth. This is often compared to a “kiss.”

Once the eggs are gathered into the male’s mouth, 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 a peaceful environment is maintained during the incubation period. If the male becomes stressed, he can swallow the eggs. The female can be removed from the tank, if the male is stressed by her presence. Adding new aquarium decor should be avoided during this time.

The water quality must be maintained during the incubation period. However, there should be very little waste being produced, if the male is isolated in a breeding tank. If water changes are necessary, only small water changes should be done very carefully.

After 30-35 days of incubation, small Betta Macrostoma fry will be released. They will range from 0.2 to 0.3 inches in length. Since the fry are tiny, they are susceptible to being eaten by their parents. If there is dense plant coverage, the fry should remain protected and safe as they would in a natural habitat. Removing the parents from the tank may increase the survival rate of the fry as well. A dedicated grow out tank would allow the fry to grow quickly as well.

Nutrition plays a critical role in the optimal growth and overall health of the fry. A good diet for the Betta Macrostoma fry would include microworms, vinegar eels, grindal worms, white worms, baby brine shrimp, and daphnia (water fleas).

Fry are more sensitive to water parameters than adult Betta Macrostoma. Therefore, it is important to monitor the water quality and temperature regularly. In addition, fry are known to release growth inhibiting hormone into the water. This can halt the growth of other fry, especially if the hormone builds up in the water. Therefore, regular water changes is important. A daily 10% water change would be ideal.

Under proper care, the fry will grow rapidly. At around two months of age, they will start to exhibit their colors. The colors and patterns will gradually become more prominent, which will help distinguish the males and females. Eventually, the males will start to show aggressive behavior towards each other. At this time, they should be separated or moved to a larger tank.

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With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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