Introduction to Trigonostigma
Many aquarists will recognize the fish from the genus Trigonostigma. In fact, you can find them almost anywhere, from local fish stores to online retailers. This is because their small size and peaceful nature have made them a popular choice for community aquariums.
Characteristics of Trigonostigma Fish
Trigonostigma fish are adaptable, feeding on prepared and frozen foods commonly used in community aquariums. Here are some key characteristics of these fish:
• Small size: Most Trigonostigma species reach a maximum length of 5cm (2″). • Peaceful nature: They are generally easy-going and can be kept in small groups. • Neutral colors: They display a range of colors, including pink, orange, copper, and grey, depending on the species. • Shoaling behavior: Many species of Trigonostigma are shoaling fish, making them perfect for aquariums with plenty of hiding places.
The Classic Harlequin Rasbora
The classic harlequin rasbora is one of the most recognizable species in the Trigonostigma genus. Trigonostigma heteromorpha is its scientific name, and it is found in the wild in Southeast Asia, particularly in the Malay Peninsula, Singapore, Sumatra, and several smaller islands.
Native Habitat
These fish inhabit slow-moving forest streams with plenty of aquatic vegetation, including Crypts. They are also found in areas with moderate water hardness and a pH range of 6.5-7.5.
Coloration
The pink-orange coloration and dark black triangular marking make the harlequin rasbora stand out against a background of live plants. However, captive strains are available, including the purple harlequin rasbora, which displays a unique purple color.
Tank Requirements
The classic harlequin rasbora is suitable for small aquariums, such as 60cm (24″) tanks. Since most fish in the hobby are captive-bred, they are relatively hardy. However, they require water that is not extremely hard, and the pH should not exceed 7.5.
The Copper Harlequin or Lambchop Rasbora
The copper harlequin, or lambchop rasbora, is another popular species within the Trigonostigma genus. Trigonostigma espei is its scientific name, and it is found in the wild in Thailand and Cambodia.
Native Habitat
These fish inhabit both slightly acidic forest streams and alkaline, limestone pools in their natural range. The latter is found only in the Krabi province of southern Thailand.
Coloration
The copper harlequin rasbora has vivid copper hues that surround the thinner black triangular marking, giving it a “lambchop” appearance.
Tank Requirements
The copper harlequin rasbora is smaller than the classic harlequin, reaching a maximum length of 4cm (1.5″). They are suitable for smaller aquariums, such as 2-foot tanks, but a slightly larger group size is recommended.
The Glowlight Rasbora
The glowlight rasbora is a popular species within the Trigonostigma genus, despite its lack of bright colors. Trigonostigma hengeli displays a pale, almost grey base color, but has a distinctive bright orange stripe along the upper edge of the black marking on its flanks.
Native Habitat
These fish inhabit similar habitats to the harlequin rasbora, particularly in Sumatra and Western Borneo.
Coloration
The glowlight rasbora has a bright orange stripe that is incredibly eye-catching, especially when they are kept in a shoal.
Tank Requirements
The glowlight rasbora is suitable for small aquariums, such as 60-liter (13-gallon) tanks. They are relatively small, reaching a maximum length of 3cm (1.2″).
Trigonostigma Somphongsi
Trigonostigma somphongsi is a rare species within the Trigonostigma genus, listed as Critically Endangered by the IUCN. It is found in small pockets of flooded fields in Thailand.
Native Habitat
These fish are well-suited to life in an aquarium, particularly in aquatic plants and botanicals.
Coloration
Trigonostigma somphongsi lack the triangular/lambchop-shaped black mark, instead displaying a dark lateral stripe.
Tank Requirements
Trigonostigma somphongsi are suitable for small aquariums, such as 45cm (18″) tanks. They are relatively small, reaching a maximum length of 3cm (1.2″).
The New Kid on the Block: Trigonostigma truncata
Trigonostigma truncata is a relatively new species within the Trigonostigma genus, discovered in 2020. It is found in lowland swamp streams from Southern Thailand to the Malayan state of Terengganu.
Native Habitat
These fish inhabit areas with moderate water hardness and a pH range of 6.5-7.5.
Coloration
Trigonostigma truncata has a distinctive “truncated” black mark, which extends right down to the caudal peduncle (where the tail meets the body).
Tank Requirements
Trigonostigma truncata is suitable for small aquariums, such as 60-liter (13-gallon) tanks. They are relatively small, reaching a maximum length of 3cm (1.2″).
Conclusion
The Trigonostigma genus of rasboras is a diverse and fascinating group of fish, with many species to choose from. By understanding their characteristics, native habitats, and coloration, you can make an informed decision when selecting the best species for your aquarium. Whether you’re a seasoned aquarist or just starting out, the Trigonostigma genus offers a range of options for anyone looking to add some excitement to their aquarium.