Common Name:  “Mahachi betta”

Scientific Namebetta sp. “mahachi” (still being classified, no official scientific name)

Often Confused With: Betta smaragdina, Betta splendens wild-type plakat, and Betta imbellis

Description:  Mature males have a very dark, almost black body, covered in a gorgeous metallic green iridescence.  While females generally have the typical brown body like other betta species, they also possess some iridescence, and the occasional specimen, particularly during spawning, is as gorgeous as the male.  Mature males nearly always have bright red eyes and a spade-shaped tail. Both sexes have a faint red wash to the fins, although it is rarely as intense or as bright as that of wild splendens.  Mature adults seem to be the largest member of the splendens complex, with slender bodies longer than that of splendens or smaragdina, easily reaching over 2 inches.  The body shape is also somewhat different, with a sloping head and a slight humpback, giving them a figure that more resembles a dolphin or a killer whale than the average betta. This shape gets more prominent as the fish age.

Maximum Adult Size
:  2 inches plus.

Area of Origin: A single somewhat brackish swamp half an hour outside of Bangkok, Thailand.

Lifespan:  Unknown, assumed to average 2-5 years like the rest of the splendens complex.

Suggested Care Level: Intermediate.  Anyone who has bred and raised Betta splendens should have no trouble with the Mahachai, but they are rare and just finicky enough they are not recommended for absolute beginners to the aquarium hobby.

Min/Max Tank Size: A 10-gallon tank, filled with about 4-5 inches of water, is perfect for a breeding pair or trio and their young offspring.  A 20 makes a great grow-out tank for an older spawn.  Mahachai should NEVER be kept in jars like splendens can tolerate, as the stress is often fatal—if they don’t find a way to jump through the tiniest possible opening, they may dash about the jar and into the glass, causing injury, or simply refuse to take any food while they feel threatened.

Temperature:   76-78 is ideal, but 72-80 will be tolerated.

pH:  7.0 – 7.8 This betta likes its pH higher than most.  The ideal range is between 7.4-7.6.  If these bettas are kept in water below a neutral 7.0 they fail to thrive and will not spawn.

Hardness:  Water should be slightly hard, although this species is not incredibly picky.

Salinity:  Their native waters are somewhat brackish, and even captive generations seem to thrive and breed best with some salt in the water.  1 teaspoon per 4-5 gallons seems to be the desired amount for breeding.  (They will live in fresh water easily, but are much less likely to breed in the total absence of salt.)

Current: This species is entirely indifferent to current when being maintained in a mixed tank.  In a breeding tank, little to no current is vital as the mahachi is a bubble nester and too much water movement will destroy any attempt to nest and breed.  In a breeding tank, a sponge filter or a corner box filter on very low power is more than sufficient.  If the male won’t nest or the nest is weak and breaks apart, turn off all current and filters.

Diet: Wild-caught Mahachai almost always demand live food to begin with.  Tubifex (or blackworms), mosquito larvae, brine shrimp, and daphnia are excellent choices.  Wilds can usually be weaned onto frozen foods (bloodworms, daphnia, brine shrimp, and the like) but will rarely accept flake or pellet foods.  F1 and further captive generations, although they need live food as fry, can be fairly easily weaned onto most prepared dry foods.

Temperament:  Fairly peaceful and even shy, although males are territorial.  Unlike most betta species, multiple males of the mahachai can be maintained together in the same tank with minimal aggression.  The mahachai is often shy of any movement from fish or people and will dart away to hide if they are startled.

Suggested tank mates:  Mahachai can be housed with most community species, although they may harass small tetras and guppies, and will be bullied by barbs, gouramis, and Betta splendens.  However, since this fish is at risk, maintaining them in a species-only tank is recommended. 

Sexing: Males are nearly black with a heavy green iridescence, red eyes, and a longer spade-shaped tail.   Females are slimmer and brown, with horizontal dark stripes and a black dot on each side of the tail base, when not in breeding dress.  They also have a visible ovipositor between the ventral fins.  Breeding dress in females, like most other bettas, is vertical white or cream barring over the brown background with the dark horizontal bars completely faded. 

Breeding:   Spawning Mahachai is very similar to spawning other splendens-complex bubble nesters.  The males build a bubble nest on the surface, and the flaring courtship is identical.  The spawning also proceeds the same way, with the female displaying courtship bars and hanging head down under the nest, where the male will wrap around her and squeeze eggs out of her in a spawning embrace repeatedly. 

However, unlike most splendens-complex bettas, the female does not need to be removed.  In fact, if left in the tank, they will spawn again regularly.  Unlike splendens, Mahachai males tending a nest are not monogamous—they have been known to spawn with two or three females back to back, just hours apart, and will often have eggs and fry of different ages in the nest at once.  Even unrelated adults seem to completely ignore the fry when they are free-swimming, so are not a threat.

Rearing fry is also very similar to that of splendens in that they need live food, frequently and in large quantity, for at least the first month.  The fry are smaller than splendens when they hatch, and may not be able to take baby brine shrimp immediately, so another food source such as microworms, vinegar eels, or infusoria should be available.  They seem more active and better at finding food than splendens fry, and can often manage on their own just eating micro-organisms living in the tank. (The addition of a Pomacea bridgesii or two to the tank can help with the microcultures.)  Mahachai are, as a whole, slow growers.   A batch of 4-5 month old Mahachai fry are generally still at or under an inch long and may be barely sexable, where most Betta splendens would be well on their way to adult size and finnage at the same age.

Personal observations, Advice
: Betta sp. “mahachai” is a beautiful wild betta of the splendens complex that needs the immediate attention of the hobbyist to preserve its existence.  Mahachai is one of the “newer” bettas to be discovered, and has not yet been officially classified as it is still being studied to verify its identity as a unique species or a morph, sub-species, or hybrid of the wild-type Betta Splendens. However, the limited habitat is rapidly being destroyed due to massive commercial development, and there is a very real concern that this species may become extinct in the wild before it receives its official scientific classification. Its captive breeding is a priority to the International Betta Congress’ Species Maintenance Program, and should be to any hobbyist who favors the betta as well.

Mahachai are best kept and spawned in a single-species tank.  A 10-gallon tank with a secure hood, outfitted with a gentle corner box or sponge filter, is perfect. The tank should not be filled all the way, but rather just enough to cover the tube of the filter.  Most bubble nesters are uncomfortable spawning in deep water, and Mahachai is no exception.   Substrate should be fine gravel, or better, silica sand. Many, many hiding places should be provided—pieces of African root wood are especially appreciated, and lava rock and shattered pieces of flowerpots also make good choices. Leaf litter on the bottom, particularly Indian Almond leaf, helps the tank a lot, providing hiding places, adding tannins to the water, and darkening the water enough to keep the fish much calmer.  Crystal clear water seems to cause the fish unnecessary amounts of stress. 

Due to the salt in the water, most plants do not thrive, however Java moss and Java fern are always options, and duckweed does alright although it never gets growing aggressively like it does in fresh water. The addition of “lucky bamboo” (Dracaena sanderana), commonly available   as a decorative, non-aquatic plant, completes the habitat. Not only will it still thrive in the lightly brackish water, having  a small stand planted in the corner diagonal from the filter provides an optimal spawning location.  Mahachai in their natural habitat spawn in tiny spaces between stalks of true bamboo and other aquatic plants. They do not prefer spawning in open water beneath a floating leaf, like Splendens often do.  The tighter, more defensible space they can wedge a nest into, the happier they are.

Mahachai are an easy keeper, a fairly easy spawner, an extremely rewarding, absolutely beautiful fish, and a great addition to any wild betta fancier’s fish room.



If you search online, you will find this article, word for word, printed here: under the title "Introducing the Mahachai Betta".  It's my article. It was initially written for the Silicon Valley Aquarium Society newsletter, and reproduced here.

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