Betta Macrostoma

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Information and general care

Macrostoma is from the Greek macro = large in extent and stoma = mouth. In other words, wide or big mouth which is a reference to its wide mouth which is an adaptation to brooding eggs and fry.
Betta macrostoma is a relative of betta splendens (Siamese fighting fish). However unlike its near relative the males do not fight to the death although there is a bit of posturing and fighting. Keep them in a large aquarium and keep an eye on the males for any excessive bullying. Be prepared to remove or partion off bullied males. Keep the aquarium at around 70F. Feed with live and frozen food and some high quality pellet food.
Macrostoma is a mouthbrooder, where the male takes the fertilised eggs in his mouth and broods them for up to a month until they become free swimming. This is an adaptation to living in rivers where a bubble nest would get swept away as would the young fry.
Make sure their maintenance tank and breeding tank has a reasonable water flow. Always keep a tightly fitted lid because they are jumpers and will accurately jump through small holes to freedom.
The male is more colourful. He is a brown/tan colour with a tail and dorsal fin that are multicoloured and looked like wide spread chinese brocaded fans. The female has the two horizontal bands familiar to betta splendens owners.
Macrostoma is elongated – torpedo shaped with small round dorsal and tail fins. The veil (anal fin) is only half as deep compared to betta splendens veil but the same length.
Macrostoma is very rare. They inhabitat a small area in Borneo. At one point they were thought to be extinct for 50 years. The Sultan of Brunei has declared the macrostoma a protected species. It is illegal to catch, keep or sell the fish in Brunei. They are also banned from export.
Macrostoma likes acidic water ranging from 5-6 ph with quite soft water. Use a reverse osmosis kit to create very soft water. Mix with 10% tap water. They should not be kept in high tropical temperatures. Somewhere between 70-75F is about right for them. They do not tolerate dirty water. They need a fully cycled tank with no ammonia or nitrites. Frequent water changes are also a must.

Preparation for breeding

When you see a pair that seem interested in each other then move them to the breeding tank. Raise the temperature of the breeding tank slowly to 74F. Make sure that they are both healthy and full bodied. Place some dried leaves in the tank. Move two sponge filters with them. Lower the breeding tank water to a depth of 6 inches. Their eggs sink much the same way as betta splendens eggs. If the eggs fall into gravel they are usually lost so a bare bottom tank is a must. Feed them well with live food, especially mosquito larvae and adult brine shrimps. Do 10% water changes every couple of days.

Betta macrostoma breeding behaviours

When the male’s colours become more intense mating will follow soon. His body will be a brighter brown/tan and the black in his fins becomes darker. The male will approach the female and present his side to her. He will arch his body towards her to present his side and fully stretch his fins. The female in response will do a snake like dance. Typically she will close her dorsal fin as she approaches him. Then they approach each other and curve their body with their heads across the other’s flank. They will do this a few practice times.

Eventually the male does the anabantid clench where he wraps his body around the female turning her in the process. Because of his long length the male will actually touch the tip of his nose to the tip of his tail in a complete circle around the female. It is only in this complete clinch and squeeze that the female release a batch of eggs which the male fertilises. The male is stunned at this point. He stays in a bent sideways position. The eggs are usually in his cupped anal fin for a few seconds. The female will drop down and start to head for the eggs. If she is lucky she will pick them from his anal fin or when they drift down or even when they land on the tank bottom. Some eggs might be lost when they hit the bottom. The eggs are quite large and she catches most of them.

After she collects all the eggs she can find she heads towards the male who has by now recovered. They come head to head, mouth to mouth even. After a while the female will spit one or more eggs out at the males mouth, which the male immediately tries to catch. Any eggs that are missed by the male are recaught by the female. This process continues until she has given up all her eggs.
Then they will start the spawning process again. The males throat will swell with all the eggs he has taken. Eventually when the female has laid all her eggs and has given the last of her eggs to the male she will try to hide. The male will keep pestering her for more eggs but eventually he gives in and goes into mouthbrooding mode and hides. He will go noticeably paler while mouthbrooding.

Raising the fry

Do not remove the female at this point or disturb the fish. Any disturbances in the first week will cause the male to swallow his brood. Do not feed the male during this time. If he should try to eat he will swallow some of his brood too. Wait until one or two weeks later then remove the female. Take care not to disturb the male too much.
After about 3 weeks from spawning the fry will be released. Make sure you have a tight cover above the aquarium when the fry take their first gulp of air, their labyrinth lung may be damaged by cold, dry air. It is better to remove the male as well at this time.
The fry are born quite large and well developed. There should be about 10 or 20. They can eat baby brine shrimp and microworms. You must change 10% of the water every day with aged water of the same ph and hardness of the breeding tank. The fry grow quite fast. When they are about an inch long the male fry may start to bicker. At about 6 months they should be 2 inches long and sellable. Keep the best specimens. Cull any deformed fry and sell the rest. There is a demand for them.


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