Gold Harlequin Rasbora (Trigonostigma heteromorpha)

Gold Harlequin Rasbora (Trigonostigma heteromorpha) is the golden aquarium colour form of the classic Harlequin Rasbora. It keeps the familiar black wedge marking and peaceful shoaling behaviour while developing a warmer gold-to-orange body tone. It is a reliable choice for a mature planted community aquarium where a proper group can use open midwater space and shaded cover.

This product is sold by the live size option shown on the page. One quantity supplies one unsexed fish in the selected approximate size band; it is not a pre-made shoal or sexed pair. Plan the aquarium around the adult fish and a group rather than the delivery size.

Quick care

Identity and the gold colour form

The accepted species name is Trigonostigma heteromorpha. Older aquarium books and supplier lists may still use Rasbora heteromorpha, which is useful as a historical search synonym but should not be repeated through the page as if it were a different fish. “Gold” describes the selectively bred colour form rather than a separate species.

Individual fish vary naturally in the depth of the gold body colour, the shape of the dark wedge and the intensity of orange in the fins. Sex, age, hierarchy, lighting and stress all affect appearance. The gallery is representative rather than a promise of one exact pattern or colour.

Aquarium size and layout

These are active shoaling fish, so aquarium length is more useful than a tall narrow shape. Around 60 litres is a practical starting point for a small group, but 80–100 litres gives more swimming room and stability, especially where other community fish are present.

Use a planted layout with an open lane through the middle. Cryptocoryne, Java fern, Anubias, water sprite and floating plants all work well where their own requirements suit the aquarium. Wood, darker substrate and shaded edges help the fish settle and can make the gold body colour look richer without forcing unnaturally bright lighting.

Water and filtration

Keep the aquarium fully cycled with ammonia and nitrite at zero. A practical working range is around 23–28°C and pH 6.0–7.5, with soft to moderately hard water. Captive-bred fish can be adaptable, but sudden changes are still stressful. In UK homes, use a reliable heater unless the room can genuinely keep the aquarium within the fish’s range throughout the year.

Gentle-to-moderate filtration and good surface movement are ideal. Harlequins do not need a powerful river current. Match the flow to the whole community and keep enough circulation to prevent waste collecting behind hardscape.

Group size and behaviour

Gold Harlequin Rasboras should be kept as a proper social group. We recommend at least eight, with ten or more creating a more confident and natural display where the aquarium is large enough. A good group spreads normal social interaction and makes the fish less likely to hide or look washed out.

They normally occupy the middle levels and are not territorial. Short display chases can occur, but persistent isolation, clamped fins or one fish repeatedly hiding away from the group should trigger a check of water quality, group size and tank mates.

Feeding

Use a good-quality small flake, micro-pellet or slow-sinking granule as the staple. Rotate suitable frozen or live foods such as daphnia, cyclops and Artemia for variety. Food size matters: small mouth-friendly particles reduce waste and let every fish feed efficiently.

Feed modest portions once or twice daily, spreading food across the surface rather than dropping everything in one place. Remove uneaten food and reduce the next portion if the group is not clearing it quickly.

Tank mates

Suitable companions include peaceful tetras, other small rasboras, Corydoras and gentle bottom-dwellers that share similar temperature and water chemistry. Calm gouramis can also work in a suitably sized planted aquarium where their individual temperament is appropriate.

Avoid large predators, persistent fin-nippers and fish that require very different chemistry. Adult angelfish and larger cichlids may view small rasboras as prey. Adult ornamental shrimp can coexist in many planted displays, but tiny shrimplets may be eaten and should not be treated as guaranteed safe.

Sexing and breeding

Mature females are generally fuller-bodied, while males tend to be slimmer and may show a sharper wedge profile. Young retail fish can be difficult to sex confidently, so this listing does not promise sex.

Harlequin Rasboras are unusual among many small cyprinids because the female often places adhesive eggs on the underside of broad leaves. Breeding is normally attempted in a separate, mature aquarium with soft, slightly acidic water and broad-leaved plants. Adults provide no parental care and may eat the eggs, so breeders normally separate the adults after spawning.

Health and acclimation

A healthy settled fish should shoal normally, feed readily, hold open fins and breathe evenly. Faded colour immediately after transport can be normal; persistent clamped fins, rapid breathing, white spots, lesions or refusal to feed require investigation.

Quarantine new fish where a suitable cycled system is available. During acclimation, avoid large temperature or chemistry changes and keep the lights subdued. Test ammonia and nitrite during the first week after adding a group to an established community.

Mobile-friendly buying summary

• What you receive: one unsexed Gold Harlequin Rasbora in the selected size.
• Plan for: a group of at least eight.
• Best home: mature planted community aquarium with open midwater space.
• Water: warm, stable and generally soft to moderately hard.
• Current price and stock: use the live selector on this page; fixed prices are not repeated in the care guide.

Before ordering

Choose Gold Harlequin Rasboras if you want a peaceful shoaling fish for a mature planted aquarium and have room for a proper group. Reconsider if the aquarium is newly cycled, very small, strongly alkaline without a measured plan, or contains predatory or aggressive fish.

The description deliberately uses natural UK aquarium wording and keeps useful synonyms in context rather than repeating search queries. That makes the page easier to scan on mobile while still giving search engines and shopping systems clear information about identity, adult size, group needs, water, diet and compatibility.