Harlequin Rasbora Care Guide: Tank Size, Diet & Tankmates
The harlequin rasbora is one of the all-time great beginner fish: peaceful, hardy, endlessly active, and dressed in a warm copper body with that unmistakable black "pork chop" wedge near the tail. It is a true community classic that has been a hobby staple for generations. At Tropical Treasures we keep the Harlequin Rasbora (Trigonostigma heteromorpha) in stock most of the time, and we usually have several of its cousins swimming nearby too. Stock rotates as fish arrive, so message us or stop by to see exactly what is available the day you visit.
Meet the harlequin rasbora
Harlequin rasboras are small cyprinids that reach about 1.5 to 2 inches, with females running slightly rounder than the more slender males. They are shoaling fish that look and behave their best in groups, weaving through the middle of the tank in a loose, shimmering school. Because they stay small and stick to open water, they pair wonderfully with bottom dwellers and shrimp that use the rest of the tank. If you love this look, you will enjoy our wider rasbora collection and the full nano fish section.
Tank Size and Setup
A group of harlequins is happy in a 10-gallon tank, though a 20-gallon long gives them more room to school and lets you keep a larger, more impressive group. These are schooling fish, so always keep at least 6 to 8 together—a lonely rasbora is a stressed, washed-out rasbora. They show their best color over darker substrate in a planted tank with some open swimming space in the middle. Live plants, driftwood, and a gentle current recreate the soft, shaded streams they come from and bring out that deep copper-orange.
Water Parameters and Heating
Harlequin rasboras are tropical fish that do best at 73 to 82°F, a pH of roughly 6.0 to 7.5, and soft to moderately hard water. They are genuinely forgiving once acclimated, which is a big part of why they are recommended for beginners, but they still appreciate stable, clean water with regular partial water changes. Like most small fish, they are sensitive to big swings, so aim for consistency over chasing perfect numbers. A reliable heater and a cycled filter are really all the equipment you need.
Feeding Your Harlequin Rasbora
These rasboras are easy eaters that accept a wide range of small foods. A quality flake or a small pellet such as the Xtreme Nano pellet or Aquarium Co-Op Magic Small Fish Feed makes a great daily staple, and you can browse more options in our flake food and frozen food collections. Feed small amounts once or twice a day, only what they finish in a couple of minutes. Occasional treats of frozen or live foods like daphnia and baby brine shrimp will boost color and condition, especially if you ever want to spawn them.
Tankmates and Temperament
Harlequins are gentle, social fish that never bother their neighbors, which makes them one of the easiest centerpieces for a peaceful community tank. They mix beautifully with other small, calm species and shoaling fish, and they pair especially well with peaceful bottom dwellers and invertebrates. Try a group with pygmy corydoras, a colony of Neocaridina cherry shrimp from our shrimp collection, and an algae crew like the otocinclus. Other small cyprinids from the danios, rasboras & barbs group, including the tiny chili rasbora, phoenix rasbora, and bigger scissortail rasbora, all make natural companions. Avoid large or aggressive fish and notorious fin-nippers that could harass them.
Is the Harlequin Rasbora Right for You?
If you want a colorful, peaceful, beginner-friendly schooling fish that thrives in a planted community tank, the harlequin rasbora is hard to beat. It is forgiving of small mistakes, gets along with nearly everyone, and looks fantastic in a group. About the only thing to avoid is keeping too few—these are not solo fish. For ideas on building the rest of a calm nano setup, our guide to peaceful nano community tankmates is a great next read, and if you eventually want a gentle centerpiece cichlid, the kribensis is a friendly step up.
Frequently Asked Questions
How many harlequin rasboras should I keep together? At least 6 to 8, and more is better. They are schooling fish that feel secure and show the best color and behavior in a decent-sized group.
Are harlequin rasboras good for beginners? Yes—they are among the hardiest and most forgiving community fish, which is exactly why they are so widely recommended for new aquarists.
Will harlequin rasboras eat my shrimp? Adult cherry shrimp are safe with harlequins. They are too small to threaten grown shrimp, though like most fish they may eat tiny shrimplets, so provide plenty of plants and cover for babies to hide.