Harlequin Rasbora (Trigonostigma heteromorpha)

The harlequin rasbora is a widely popular schooling fish in freshwater aquariums. Hailing from forest pools and streams in Southeast Asia, harlequin rasbora care is relatively easy and straightforward. In this guide we’ll cover all of the key care concepts for harlequin rasbora, including their feeding, proper water conditions, tank setup, and compatible tankmates.

Harlequin rasbora are a beloved species, being found in many local fish stores and available with many online and local sellers. Distinguished by their characteristic scarlet-red coloring and black accents, these schooling fish exhibit their best colors in groups of at least six, the larger the better. Large schools also help to reduce fish stress levels and aggression.

The harlequin rasbora is a gentle species that can live in harmony with other fish of comparable size in an aquarium community. They thrive in well planted aquariums as they tend to blend in with the environment.

Harlequin Rasbora Species Overview

Harlequin Rasbora Care

Harlequin rasbora are a beautiful aquarium fish that will thrive when provided with proper care. Their peaceful nature makes them a great addition to almost any community tank, as long as their tankmates are not substantially larger or more aggressive. Their relatively easy care requirements make them an excellent beginner fish.

Numerous other rasbora species are popular among aquarium hobbyists, such as the very similar purple harlequin rasbora. Within the hobby, harlequin rasbora are generally regarded as some of the hardiest and easiest to care for.

Feeding

Harlequin rasbora are omnivorous, and in the wild they are know to primarily feed on insects. While flakes or pellets can be the staple in an aquarium, it’s beneficial to supplement their diet with a variety of foods. This can include live or frozen foods like brine shrimp, daphnia, or bloodworms. These additions mimic their natural diet and help to provide essential nutrients.

Pay attention to their behavior and adjust the feeding routine accordingly. We’d recommend feeding no more than once daily and to avoid overfeeding, as it can lead to water quality issues and bloating. Feed only what they can consume in a minute or two.

Water Conditions

Maintain stable and optimal water conditions when caring for rasbora. Harlequin rasbora prefer slightly acidic to neutral water with a pH range of 6.0 to 7.8. Keep the water temperature between 70°F to 82°F (21°C to 28°C).

Harlequin rasbora come from waters with lots of leaf litter and plant debris, resulting in lots of tannins and dark water. You can try to mimic this environment within an aquarium by using almond leaves and drift wood, which will also help keep the water on the acidic side. Dark water and tannins are known to reduce stress levels and improve coloration in rasbora.

Regularly test and monitor water parameters, including ammonia, nitrites, nitrates, and pH. Harlequin rasbora can be sensitive to sudden drastic changes in water conditions, so be careful when adding new aquascape features or doing major water changes.

Breeding

Breeding harlequin rasbora in an aquarium can be a rewarding but somewhat challenging endeavor. You’ll want to set up a separate breeding tank to provide a controlled environment. The tank should be well-planted with fine-leaved plants or moss, creating hiding places for the eggs and fry. Use a sponge filter to provide gentle water flow.

Choose healthy and mature individuals for breeding. Harlequin rasbora form pairs during the breeding process, so it’s beneficial to have an even number of males and females. Before introducing them to the breeding tank, condition the fish with a high-quality and varied diet. Offer live or frozen foods like brine shrimp or bloodworms to enhance their nutritional status.

Increase the water temperature slightly to simulate the onset of the rainy season, which triggers breeding behavior. Keep the temperature around 78-80°F (25-27°C). Maintain optimal water conditions with an acidic pH around 6.0-6.4.

Harlequin Rasboras are egg scatterers. The female scatters her eggs among the fine-leaved plants. Once the eggs are laid, promptly remove the adult fish from the breeding tank to prevent them from consuming the eggs. The eggs are adhesive and may stick to the plants. If not, they will fall to the tank bottom. Provide a substrate of marbles or a mesh net at the tank bottom to protect the eggs from being eaten by the adults.

Fry Care

After hatching, the fry will benefit from infusoria or commercially available liquid fry food. As they grow, you can introduce newly hatched brine shrimp or micro-worms to their diet.

Regular, small water changes help maintain good water quality in the grow out tank. Be gentle during water changes to avoid disturbing the fry. They will take several months to grow to a stage in which they can be kept with adult rasbora.

Tank Setup for Harlequin Rasbora

Creating an appropriate tank setup for harlequin rasbora is essential to ensure their well-being and encourage natural behaviors. A minimum tank size of 10 gallons is suitable for a small group of harlequin rasbora. However, a larger tank such as a 20 or 29 gallon provides more swimming space and allows for a more stable environment.

Harlequin rasbora appreciate a well-planted aquarium. When aquascaping we’d recommend using live plants with broad leaves to replicate their native environment. Easy care plants like java fern, anubias, and cryptocoryne provide hiding spots for rasbora and help to create a natural feel.

As mentioned previously, you can utilize elements such as driftwood and leaf litter to help darken the water and keep the water on the acidic side. We’d also recommend an aquasoil or dirted substrate to help emulate their natural habitat.

You’ll need an appropriately sized aquarium filter and heater, and we’d also recommend using an aquarium lid when keeping harlequin rasbora as they can jump out of the aquarium.

Harlequin Rasbora Tankmates

Harlequin rasbora are peaceful and do well with other non-aggressive community fish. Avoid keeping them with larger or aggressive species that may intimidate them.

Some fish that do well in a community tank with harlequin rasbora include:

• Betta fish
• Other rasbora (Such as purple harlequin or chili rasbora)
• Neon tetra
• Panda corydoras (Or other cory catfish)

Be sure not to overstock your aquarium, we’d recommend checking out an aquarium stocking calculator such as aqadvisor.com to help gauge the stocking level of your tank.

Harlequin Rasbora Care Summary

The harlequin rasbora, with its vibrant colors and peaceful demeanor, is a delightful addition to freshwater aquariums. This care guide covers essential aspects such as feeding, water conditions, breeding, and tank setup to ensure these fish thrive in captivity.

Whether you’re a beginner or an experienced hobbyist, the hardy nature of harlequin rasbora makes them an excellent choice for community tanks. By providing the right environment, proper nutrition, and compatible tankmates, you can enjoy the beauty and social dynamics of these charming fish.