Max Size: 2.5cm

Siamese Dwarf Rasbora (Trigonostigma somphongsi)

Siamese Dwarf Rasboras are an extremely rare, beautiful and peaceful little fish that would be a fantastic addition to your aquarium, especially those with planted nano tanks. Unfortunately, these Rasboras are highly endangered due to habitat destruction in the wild, but a few breeders worldwide produce them.

It is recommended that you keep Siamese Dwarf Rasboras in schools of 10 or more individuals as this will help reduce their shy nature. In addition, the aquarium needs to be of adequate size to allow sufficient space for the school to swim around.

It is safe to keep these fish with other peaceful, small fish. Still, it is easily intimidated, so it is essential that you avoid all aggressive species, as well as larger and overly active species that may consume or scare these fish. Due to their small size and peaceful demeanour, it would probably be better to keep these fish in a species only aquarium or keep them with Dwarf Shrimp.

The aquarium setup is not especially critical; however, they will display better colouration in a heavily planted layout with a dark substrate. To obtain a more natural-looking arrangement, you should use a soft, sandy substrate with driftwood roots or branches set so that plenty of caves and shaded areas are formed.

The addition of dried leaves such as oak, beech or almond leaves are all suitable and would further accentuate the natural feel. These leaves will also encourage the growth of beneficial microbe colonies as decomposition occurs. These microbes will provide an important secondary food source for any babies, whilst other chemicals and tannins released by the decaying leaves will help simulate blackwater conditions.

Siamese Dwarf Rasboras seem to do better under reasonably dim lighting, therefore having some floating vegetation to diffuse the lighting will further benefit these fish.

Siamese Dwarf Rasboras have elongated transparent bodies that display some orange colouration when well-conditioned. In addition, these fish possess a thickish black stripe that gets slightly broader towards the anterior, and their fins are clear except for the caudal fin that may have an angular orange colouration.

Tank Mates for the Siamese Dwarf Rasbora

1 ideal tank mate ideas for the Siamese Dwarf Rasbora include:

Celestial Pearl Danio(Danio margaritatus)
Quick Facts
Scientific NameTrigonostigma somphongsi
Other NamesSomphongs's Rasbora
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 10+
Lifespan2 - 4 years
Water Parameters
Water TypeFreshwater
PH5.0 - 7.0
GH2 - 10
TDS18 -143
71 - 79℉
21.7 - 26.1℃

Photos of the Siamese Dwarf Rasbora

Siamese Dwarf Rasbora
Siamese Dwarf Rasbora
Siamese Dwarf Rasbora
Siamese Dwarf Rasbora


Siamese Dwarf Rasbora (Trigonostigma somphongsi) Species Profile & Care Guide

Natural Habitat

Siamese Dwarf Rasboras are believed to be endemic to the Mae Klong Basin near Ratchaburi province in Western Thailand. At one point, they were thought to be extinct, although they have recently been rediscovered. These fish inhabit gently flowing forest streams and tributaries where submerged aquatic plants grow thickly.

The water in their habitat is sometimes stained a brown colour due to tannins and other chemicals discharged by decomposing organic matter. Their substrate is usually covered with fallen leaves, branches, and twigs. These environments contain soft, slightly acidic to neutral water and are frequently dimly lit due to dense vegetation and the forest canopy above.

What to feed the Siamese Dwarf Rasbora

Siamese Dwarf Rasboras are unfussy and relatively easy to feed. However, for the best condition and colour of your fish, it would be better to offer them regular meals of small live and frozen foods such as daphnia, brine shrimp, cyclops, mosquito larvae and bloodworm. You will also need to provide them with high quality dried food like crushed flakes, micropellets and granules to balance their diet.

How to sex the Siamese Dwarf Rasbora

It is somewhat straightforward to differentiate between female and male Siamese Dwarf Rasboras. Mature females usually are deeper-bodied, noticeably bigger than males and remain a silvery-yellow colour. In contrast, males are slimmer, slightly smaller, and once males have settled into an aquarium, they develop a copper-orange colouration.

How to breed the Siamese Dwarf Rasbora

Like most small Cyprinids, Siamese Dwarf Rasboras exhibit no parental care, although they do use a different spawning method to most as they attach their eggs to the underside of wide plant leaves.

If your fish are in good condition, they will often spawn, and in a densely planted, established aquarium, small numbers of young may start to appear without human interference. However, if you would like to increase fry numbers, a more controlled approach will be required.

You can condition an adult group together, but you will need to set up a separate breeding tank. This tank should be dimly lit, and the bottom should either be left bare or covered with a mesh that will allow eggs to fall through if they fail to adhere to the plant but small enough so the adults cannot reach them. You can also use artificial grass type matting; this can work just as well.

The waters pH level should be between 5.0 and 6.0, and the temperature needs to be slightly higher than their regular aquarium. Good sized broad-leaved plants such as Microsorium and Cryptocoryne will also need to be added; however, filtration is unnecessary unless you prefer to add a small air-powered sponge filter.

The best way to condition Siamese Dwarf Rasboras is to feed them little amounts of live and frozen fare 2 or 3 times a day for a couple of weeks before attempting to spawn them. Then once the females are noticeably full of eggs and the males show their best colours as they display to one another, you should perform a significant, cool water change. A few hours after this water change, usually in the evening, you should place one or two pairs into the breeding tank.

Spawning will typically occur early in the morning and is led by a spurt of courtship activity by the males. After that, the couple will perform several 'dry runs' over a chosen spawning site, then several hours later, the female will begin to lay small batches of eggs. The male then fertilises the eggs before the next set is laid.

If the couples fail to spawn straight away, you can leave them where they are. However, if you do not notice any eggs after 3 or 4 days, you should return them to their usual aquarium and choose another pair.

Once all the eggs have been laid, you will need to remove the adults from the breeding tank as soon as possible; otherwise, they will consume the eggs if given a chance.

The incubation period is temperature-dependent; however, the eggs will usually hatch somewhere between 24 and 48 hours later, with the young becoming free-swimming about a week after that.

It would be best to initially feed your fry with Paramecium or similar, moving on to baby brine shrimp and microworm once your fry are large enough to accept them.

Other Rasboras of interest

Black Line Rasbora(Rasbora borapetensis)
Chilli Rasbora(Boraras Brigittae)
Clown Rasbora(Rasbora kalochroma)
Dwarf Rasbora(Boraras maculatus)
Emerald Eye Rasbora(Brevibora dorsiocellata)
Exclamation Point Rasbora(Boraras urophthalmoides)
View all Rasboras
Date Added: 12/07/2021 11:15:36 - Updated: 19/01/2022 14:23:03