Welcome, fellow aquarium enthusiasts! Are you looking for a small and colorful fish to add some personality to your tank? Then the Harlequin Rasbora (Trigonostigma heteromorpha) may just be the perfect fit. These native South East Asian fish come in striking golds, reds and blacks and are relatively easy to care which makes them an incredibly popular choice among aquarists of all experience levels. In this blog post, we’ll provide you with detailed information on what these marvelous little rasboras need – from ideal feeding habits to companion species – so that you can confidently create the perfect home for your new aquatic friends!

How the Harlequin Rasbora Looks

The harlequin rasbora is truly one of a kind. With its signature streamlined body and triangular patch that extends from the head to the tail, it stands out among other fish. 

The Harlequin Rasbora is a fish that stands out from the other Rasbora species due to its unique and standout coloration and patterns that make it easily recognizable. Harlequin Rasboras are round in shape with beautiful silvery sheens giving off an ethereal orangish hue at the center of their bodies. The most defining feature of these fish is the black triangular marking that stretches from their dorsal fin towards the caudal fin, ending right at the end of the tail. When given proper care, they can be kept as stunning additions to any established community aquariums!

These small fish will grow up to 1.75 to 2 inches (4-5 centimeters) long, but they’re able to make a big impression with their beautiful patterning and coloring. Although these fish may vary slightly in size and appearance, they are known for their distinctive black triangle that rests on a bright orange body. So if you’re looking for easy care and vibrant colors, harlequin rasboras are definitely the way to go!


Watching school of Harlequin Rasboras is like watching a colorful and graceful dance. These fish move in unison, gracefully gyrating through the water column with beauty and precision. It’s amazing to watch them together – no matter which direction they go, the school follows in harmony. If a few rasbora strays off course, soon he or she will be back in line with the rest of the group. This behavior isn’t just for show – it’s necessary for their survival since it indicates towards predators that trying to hunt just one fish will be difficult due to them being part of a larger group. It’s fascinating to watch these hardy little fish come together so peacefully!

This fish is a peaceful, schooling fish that loves to swim around and explore its environment. They can be kept in social groups, making for an interesting experience for you and your fish. As with all Rasboras, the Harlequin loves to move as a group. This group behavior is one of their main attractions – they dart around the tank in perfect synchrony, creating an ever-shifting landscape of color and movement. On top of that, these friendly little fish are undemanding and quite adaptable – making them great pets for almost any kind of aquarium hobbyist!

Aquarium Setup

Setting up a fish tank for harlequin rasbora can be an exciting and rewarding endeavor! The most important part of setting up a home for these small fish is creating a healthy environment. You’ll need to begin by selecting the right size tank, selecting the right filtration system, and adding in the proper decorations and substrate. Make sure you add in plenty of hiding spots like live plants or caves to give your harlequin rasbora some privacy. After everything is set up, introduce your best-carefully selected-harlequin rasbora into the tank, give them time to adjust, and watch as they show off their beautiful colors in their new home!

Tank Size

Deciding what size fish tank to get for your harlequin rasbora can be a tricky proposition! While they are small, schooling fish and do not require a big aquarium, they should still have enough room to swim around freely. We recommend starting with a 20-gallon tank (around 90 liters) so that your rasboras can have the space they need. If you opt for more than a small group, an extra 5-10 gallons (25-50 liters) would be ideal, or possibly even larger. Also remember to provide plenty of safe hiding spots amongst plants and other decorations – your harlequin rasbora will be much happier with some private areas away from the hustle and bustle of the tank!


Harlequin rasbora are striking, brightly colored fish that can make an excellent addition to any aquarium. They do best in a tank with good filtration, particularly if the other inhabitants tend towards being active and messy eaters. A filter that provides adequate water flow and is sized correctly for the tank will ensure an ideal environment for the harlequin rasbora. Using a combination of mechanical and biological filtration can help maintain a healthy balance in the tank and keep your finned friends happy. Keep an eye on your filter to make sure it isn’t getting clogged up or the tank becoming overgrown with algae to get the most out of your aquarium experience with these beautiful creatures!

Decorations and Plants

Decorating an aquarium can be an exciting part of creating the perfect environment for your harlequin rasbora. To best suit this fish, you should create a space full of natural materials like smooth, water-worn rocks, live plants and pieces of driftwood. Keep the decorations to a minimum to allow plenty of swimming space and enough to provide a sense of security. Add in some shade-providing plants with shorter stems such as Java fern or anubias barteri. Both are great choices for hardy and easy-to-maintain tanks! Having live plants will also help add to the richness of your tank by oxygenating the water and providing food and shelter for your happy rasbora!


Maintaining the right aquarium temperature for harlequin rasbora is one of the most important things you need to consider when setting up a tank for these beautiful fish. An ideal water temperature range for harlequin rasbora should be between 72-80 degrees Fahrenheit (22-27 Celsius). Taking the time to create healthy, stable conditions in your tank prior to introducing the fish will give them the best chance at a long, healthy, and happy life. Monitor this temperature consistently and make adjustments as needed using quality heaters and thermometers to give your harlequin rasboras the loving home they deserve.

The Harlequin Rasbora - All You Need To Know
The Harlequin Rasbora – All You Need To Know


When it comes to feeding your Harlequin Rasboras, variety is key. These omnivorous fish enjoy a diet of both plant-based and protein-based foods. You can offer them live or frozen bloodworms, brine shrimp, or daphnia, as well as dried food and/or fresh vegetables like lettuce or spinach. Feed your rasboras one to two times a day in small portions and make sure they finish everything – uneaten food can quickly dirty the tank.

Flake food is also a great way to supplement their diet, as it is full of essential vitamins and minerals that can promote the health of your fish. Just be sure to look for a good quality food.

Tank Mates

Harlequin rasbora is a very peaceful fish that can be kept in groups of six or more, so when you’re planning a tank for them, you can think about plenty of other tank mates. They are relatively peaceful and sociable fish, so it’s best to pair them with other small community fishes that share similar temperament and water parameters. Other small-sized fish work well with harlequin rasboras and make for fascinating communities. Danios, guppies, and some species of tetra are all great options to consider. Shrimps, snails, and even some Corydoras catfish can work too; most bottom-feeding fish get along perfectly with the harlequin rasbora! By adding some variety to your tank setup when choosing tank mates for your harlequin rasbora, you’ll end up with an underwater paradise – it’s always exciting to see creatures school together, browse different areas of the aquarium, and create their own mini ecosystem.


The Harlequin Rasbora is a beautiful and easy-to-care fish that makes the perfect addition to any aquarium. By following the simple guidelines laid out in this blog post, you’ll have no trouble keeping your rasboras happy and healthy for years to come. Thanks for reading and we hope this has helped you on your journey to becoming a successfully aquarist!