Harlequin Rasbora

Published August 6, 2019
Author: Mike - FishLore Admin
Social Media: FishLore on Social Media

The Harlequin Rasbora is a long time favorite for many hobbyists. The Harlequin Rasbora has the signature black triangle shape that starts at the dorsal fin and continues to the caudal fin. This fish is fairly hardy but they should only be added to tanks that have completed the aquarium nitrogen cycle. This rasbora is a schooling fish and will be happy with 6 or more of it's own kind. They make a great addition to heavily planted tanks and community tanks.

The Harlequin Rasbora is sometimes confused with the Lambchop Rasbora (Trigonostigma espei) but the Lambchop Rasbora's black region starting at the mid-section (dorsal fin) is not quite as large at the beginning of the black region and is shaped more like a "lamb chop" instead of the black triangular shape of the Harlequin.

It's always a good idea to keep any new fish in a quarantine tank for a few weeks for monitoring before introducing them into your main tank. Even though this fish is farm raised they still have to go through several holding tanks before they reach your retail store and they have been in contact with who knows what. This fish is quite poopular and are frequently available in pet stores.


The Harlequin Rasbora will accept smaller fish food including flakes, frozen, freeze dried and live fish foods.

trigonostigma heteromorpha trigonostigma heteromorpha

trigonostigma heteromorpha
Black Morph

trigonostigma heteromorpha
Blue Morph

trigonostigma heteromorpha
Gold Morph

trigonostigma heteromorpha
Gold Morph

Harlequin Rasbora Care

Scientific Name : Trigonostigma heteromorpha

Common Names : Red Rasbora, Harlequin Fish

Care Level : Easy to Moderate, but only add to a tank that has already been through the aquarium nitrogen cycle

Size : 2 inches (5 cm)

pH : 5.5 - 7.0

Temperature : 72°F - 80°F (22°C - 27°C)

Lifespan : 3 - 5 years

Origin / Habitat : Thailand

Temperament / Behavior : A peaceful fish and best kept in a small school (shoal) of 6 or more.

Breeding : They have been bred in captivity and are egg layers. Lays eggs underneath leaves.

Aquarium Size : 20 gallon minimum (schooling fish)

Tank Mates : They are a very peaceful little fish. Keep them in a small school and try not to keep them with larger fish that may be tempted to eat them or fish that may harass them.

Fish Disease : Freshwater Fish Disease

Diet / Foods : Omnivore - provide a varied diet with live food, frozen food and they should accept flake food.

Tank Region : Middle to top

Gender : Females are usually larger.

Photo Credit : Photos copyright JJPhoto.dk

Site References :

Fish Lore Forum : Harlequin Rasbora Forum

Harlequin Rasbora Comments and Tips

From: Robert
I bought 12 of these rasboras for my 55 gallon planted tank and they seemed to have developed a hierarchy of sorts... There seems to be a definite leader that the rest follows around all the time. My shoal is interesting to watch and I highly recommended them for others thinking about getting some. I feed mine mostly flake foods and sometimes give them frozen blood worms.

From: Tom
I have 5 females and 1 male Harlequin Rasbora. The leading female seems to get deep red and every night the other females seem to challenge her. I don't know if the leader has changed at all since I got them about 9 months ago.

From: Chris
We had 5 Harlequins to start with but lost one due to water problems, the 4 remaining are very entertaining especially at feeding times when they shoot up very quickly and take food from the surface. They school most of the time but sometimes seperate into two pairs. They also explore the tank in and around the plants more than some of the Tetras.

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