The Glowlight Rasbora Trigonostigma hengeli (previously Rasbora hengeli) is a pretty little fish that many aquarists fall in love with, and rightfully so. This simply-dressed fish has lots of hidden charm and is always on the move. A school of these in the aquarium creates bright little flickers of glowing color all across the upper levels of the tank.
This cyprinid was discovered in the mid-1900s and scientifically described by Meinken in 1956. It is found in Southeast Asia on the Malay Peninsula through Singapore, the Greater Sunda Islands of Borneo and Sumatra, and possibly in Thailand and Cambodia as well. These fish are wild-caught and so are rather rare, but specialized and well-stocked suppliers will often have them available.
These tiny fish only reach just over an inch (3 cm) in length but are surprisingly eye-catching in appearance. Their coloring ranges from a translucent ivory to a pink-flushed orange. In healthy specimens, the fins are a distinct lemon yellow. Their most distinguishing feature is a bright stroke of neon orange just above a thin black marking along the back half of their body. Thus, they are called Glowlight Rasbora as well as Glowing Rasbora and Hengel's Rasbora.
This fish has two close relatives with which it is often confused, the Harlequin RasboraTrigonostigma heteromorpha and the Lambchop Rasbora or Espe's Rasbora Trigonostigma espei. The Glowlight Rasbora is often mistaken for the Espe's Rasbora, and to confuse the issue more, both are sold under the name of 'False Harlequin.' To differentiate these three from each other, notice some subtle distinctions. The Espe's Rasbora should be bronze pink in color and have no orange stripe above the black triangle. The Harlequin Rasbora is pale pink to bright red, is much stockier than its cousins, and its black mark is much closer to a triangle shape.
The Glowlight Rasbora is a great fish for the beginning aquarist who wants something special for a peaceful community tank. Even more enticing than their looks is their fascinating, fast-paced lifestyle. They absolutely must be kept in a school as the companionship of their own species is essential to their well-being. Groups should be made up of at least 8 to 10 individuals. A school could be housed in a tank as small as 10 gallons, but a 20-gallon aquarium will suit them best. They are very fun to watch, even for non-aquarists, as they are almost constantly in motion, creating flashes of orange color.
This is a very forgiving fish, more so than many other rasbora species, and requires little extra care. It's an excellent species to introduce yourself or a friend to the hobby. They generally have a good disposition and can be combined with most any fish that won’t eat or frighten it, or the opposite. They also have excellent disease resistance. To bring out their best colors, use a darker substrate and provide them with plenty of plants. The tank should be carefully covered as these fish are liable to jump if startled or excited.
The Glowlight Rasbora Trigonostigma hengeli (previously Rasbora hengeli) was described by Meinken in 1956. It originates from Southeast Asia on the Malay Peninsula through Singapore, the Greater Sunda Islands of Borneo and Sumatra, and possibly in Thailand and Cambodia. This species is not listed on the IUCN Red List as it has not yet been evaluated. Other common names it is known by are Hengel's Rasbora, Glowing Rasbora, Rasbora hengeli, False Harlequin, and Lamb Chop Rasbora.
There are currently four distinct members in the Trigonostigma genus. These fish were previously contained in the Rasbora genus but were reclassified in 1999 by Kottelat and Witte. They were distinguished by their triangular-shaped pattern and coloring, as well as their reproductive method of depositing adhesive eggs underneath leaves or other matter rather than simply scattering them.
In nature, these fish are found in huge groups, filling entire sluggish streams. These heavily-vegetated, peaceful waters are calm or gently flowing. Often, decomposing organic debris stains the water a yellowish-brown with tannins and other chemicals. The water is soft and weakly acidic or neutral, and well-shaded by forest canopies. These fish swim in schools and are micro-predators, feeding on small insects, worms, crustaceans, and zooplankton.
Scientific Name: Trigonostigma hengeli
Social Grouping: Groups
IUCN Red List: NE - Not Evaluated or not listed
The Glowlight Rasbora is a small, slender fish, reaching a total length of just over 1 inch (3 cm). It has a typical lifespan of 2 to 3 years with good care. The body color ranges from translucent ivory to a pink flushed orange. In healthy specimens, the fins are a distinct lemon yellow. The most distinguishing feature is a thin black marking, above which is a stroke of neon orange.
Size of fish - inches: 1.2 inches (3.00 cm)
Lifespan: 2 years - They have an average lifespan of about 2 to 3 years with proper care.
Fish Keeping Difficulty
This very hardy fish is more forgiving than many other rasbora species, making it an ideal first rasbora and great for beginning aquarists. They are usually not very picky eaters and will accept and thrive on quality flake foods. With well-filtered water and regular maintenance, these fish do very well, but they must be kept in a school.
Aquarium Hardiness: Very Hardy
Aquarist Experience Level: Beginner
Foods and Feeding
The Glowlight Rasboras are omnivores. In the wild, they feed on small insects, worms, crustaceans, and zooplankton. In the aquarium, their diet should be based around a quality flake or pellet food supplemented with the occasional live snack like brine shrimp or bloodworms. Some blanched lettuce or spinach is also a welcome addition to their diet.
Feeding time with rasboras is especially fun to watch. They will dart to the surface, grab some food, and then dive an inch or so and swallow. They repeat this until the food is gone. These fish will do best when offered food several times a day, but only offer what they can eat in 3 minutes or less at each feeding. If you feed only once per day, provide what they can eat in about 5 minutes.
Diet Type: Omnivore
Flake Food: Yes
Tablet / Pellet: Yes
Live foods (fishes, shrimps, worms): Some of Diet
Vegetable Food: Some of Diet
Meaty Food: Some of Diet
Feeding Frequency: Several feedings per day - Offer only what they can consume in 3 minutes or less with multiple feedings per day.
These fish are not exceptionally difficult to care for provided their water is kept clean. At least 25 to 50% of the tank water should be replaced once a month. If the tank is densely stocked, 20 to 25% should be replaced weekly or every other week. The substrate should also be vacuumed during water changes to avoid accumulation of waste.
Water Changes: Monthly - If the tank is densely stocked, water changes should be done every other week.
The Glowlight Rasbora is a schooling species that rarely leaves the upper and middle regions of the aquarium, not even to chase after food. This fairly hardy fish will adapt to most aquarium conditions. A school of 8 to 10 can be kept in a smaller, 10-gallon aquarium, but they will do best in about a 20-gallon tank. The Glowlight Rasbora's colors can be quite stunning and will show best in soft, slightly acidic water conditions. Provide a good filter, but as these fish come from very sluggish waters, strong filtration is not necessary. The tank should be carefully covered because these fish are liable to jump if startled or excited.
A heavily-planted tank will make them feel much more at home. A good aquascape would be dense plantings reaching the surface of the aquarium around the sides and back with a few broad-leaved plants for shelter. Leave plenty of open water in the middle for swimming. A dark substrate and areas of shadow will bring out their best colors. Adding floating plants will give the fish extra security and help to diffuse the light entering the tank. Bogwood is also a great addition as the tannins help maintain water parameters more closely resembling their natural environment. To create a natural feel and encourage the growth of microbe colonies, add dried leaves to the tank. The microbe colonies will also act as a secondary food source.
Minimum Tank Size: 10 gal (38 L) - Though a school can be kept in a smaller aquarium, they will do best in about a 20-gallon size.
Suitable for Nano Tank: Yes
Substrate Type: Any
Lighting Needs: Moderate - normal lighting
Temperature: 73.0 to 82.0° F (22.8 to 27.8° C) - Suggested breeding temperatures are between 77 and 82.4° F (25 - 28° C).
Breeding Temperature: 77.0° F - Breeding temperatures suggested are between 77 and 82.4° F (25 - 28° C).
Range ph: 6.0-7.5
Hardness Range: 1 - 15 dGH
Water Movement: Moderate
Water Region: All - They will rarely leave the upper and middle regions of the aquarium.
These fish must be kept in groups of at least 8 or more. Although they are technically a schooling fish, they tend to swim about in loosely-formed groups unless they are frightened. The more fish you have, the more apparent the schooling instinct will become. They will establish a pecking order but never really cause harm to each other. The males will display their best colors as they compete for the attention of females.
The Glowlight Rasbora is a good community fish and will get along with most tankmates that don’t mind an active environment. They are small, however, and can easily be eaten by bigger tankmates. Good tankmates include many popular community fish. Cyprinids are especially good as well as some of the characins like tetras, live bearers like mollies, guppies, plates, and swordtail fish. They also do well with bottom-dwelling peaceful catfish and loaches, and even some of the dwarf cichlids.
Temperament: Peaceful - These peaceful fish will get nervous with larger tankmates.
Same species - conspecifics: Yes - This fish must be kept in a school of 8 to 10, or more, of its own kind.
Peaceful fish (): Safe
Semi-Aggressive (): Threat - Should be kept with peaceful community fish only.
Aggressive (): Threat
Large Semi-Aggressive (): Threat
Large Aggressive, Predatory (): Threat
Slow Swimmers & Eaters (): Safe
Shrimps, Crabs, Snails: Safe - not aggressive
Sex: Sexual differences
The Glowlight Rasbora can be very difficult to sex. However, mature females are usually deeper-bodied and larger than the males. Males will be more slender and more brightly colored.
Breeding / Reproduction
Breeding the Glowlight Rasbora can be a bit challenging, but there are few reports of successful aquarium spawnings. If kept in a well-maintained aquarium with dense planting, you may see some young fish showing up. Like the other cyprinids, they exhibit no parental care for the young, but they differ slightly in their spawning method. Instead of scattering their eggs in open water, they attach the eggs to the undersides of broad-leaved plants or other objects.
This overall approach for breeding Trigonostigma spp. is based on the Espe’s Rasbora with a controlled spawning. One or two pairs should be well-conditioned with small offerings of live foods several times a day, usually for about 4 weeks. Conditioning with live foods will also bring out the male's color. When well fed, mature females should begin filling out with eggs.
Provide a dimly lit breeding tank and keep the water level low, at about 6 to 8" (15 - 20 cm). The water should be very soft at about 2° dGH, slightly acidic with a pH of 5.3 to 5.7, and a temperature between 77 and 82.4° F (25 - 28° C). Filtration isn't really necessary, but you can add a small air-powered sponge filter or some peat filtration. They need either artificial or live broad-leaved plants, like Microsorium or Cryptocoryne, for the eggs to adhere to. A spawning mop can also be added to catch any eggs that don't attach to the leaves and keep them out of the reach of the parents.
Place one or two pairs in the breeding tank, and spawning will usually occur in the morning hours. The male will direct the female to his selected location, almost always the underside of a broad-leaved plant. The male performs a courtship dance, and the spawn takes place under the plant leaves, with the partners swimming upside down. After the spawn, remove the parents as they will eat the eggs and darken the tank. At this time, lower the water level to between 4 and 6 inches (10-15 cm), taking care to keep the eggs below the surface.
The fry will hatch in about 24 hours and be free-swimming in about 7 to 14 days. Feed the free-swimming fry starter foods like infusoria for the first few days until they are large enough to eat baby brine shrimp. See Fish Food for Fry for information about types of foods for raising the young.
Ease of Breeding: Moderate - Breeding is probably similar to its close relatives, the Espe’s Rasbora and the Harlequin Rasbora.
Glowlight Rasboras are very hardy, and disease is not usually a problem in a well-maintained aquarium.
Some diseases that are common in rasboras are dropsy, fin rot, and Ich if good water quality, nutrition, and maintenance is not provided. Remember that any additions to a tank, such as new fish, plants, substrates, and decorations, can introduce disease. Properly clean or quarantine anything that you want add to an established tank so as not to upset the balance.
These fish are very resilient, but knowing the signs of illness, and catching and treating them early makes a huge difference. An outbreak of disease can often be limited to just one or a few fishes if dealt with at an early stage. The best way to proactively prevent disease is to give your fish the proper environment and a well-balanced diet. The more closely their environment resembles their natural habitat, the less stress the fish will have, making them healthier and happier. A stressed fish is more likely to acquire disease. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.
The Glowlight Rasbora is reasonably priced and fairly difficult to come by, though specialized suppliers and well-stocked fish stores will carry them.
Gaina - 2016-03-05 Not a stupid question at all. Some species of fish that live in deeper parts of the ocean posses something called bioluminescence to glow in the dark, mainly to catch food. Rasbora, however, don't have this ability.
Anonymous - 2008-05-03 I literally just got them (10 minutes at max) in my tank and they are already schooling! I have 2 Leopard Danios, 4 Glowlight Tetras, 2 Paleatus Cories(non-albino), 12 Cardinal Tetras, and now 5 Glowlight Rasboras. And one of them when it first got in the tank thought the Glowlight Tetras were its school!