Harlequin Rasbora Care Guide

Rasbora heteromorpha

Difficulty	Easy
Minimum Tank Size	10 Gallons
Diet	Omnivore
Water Parameters	75-82 F, pH 6.5-7.5
Aggression	Peaceful
Size	2"

Harlequin Rasbora are hardy freshwater fish that make for excellent starter fish. They stay small, bring color to the tank and are very peaceful fish. They do best when placed in a tank as a small school, over six fish. This gives them a group to swim around the tank in and feed together. They can be kept solo, however this is one of the easier fish to start schools with, so I highly recommend getting several right at the start.

To keep a school of 10 rasbora use a 15 gallon or larger tank to make sure they have adequate space once the plants and substrate have been added to the tank.

On average Harlequin Rasbora will live for over three years. Again they are hardy fish, so as long as you keep the tanks water parameters consistent they should live over five or six years.

Behavior & Aggression

There is very little aggression from these fish. Occasionally you may see some of the males competing with one another to establish dominance, however these fights tend to be short and without any injury. The losing fish will often retreat and spend more time swimming among the plants, hiding in their leaves. They do like big open spaces to swim around in their schools. Lone fish can be kept in smaller tanks, however I recommend no smaller than 10 gallons if you plan on keeping a school.

Small, younger members of the school will also hide in plant leaves, but after they mature and become more comfortable in the tank you can expect to see them emerge from the plants and join the school.

These fish love to swim around big leaf plants, as they use these for breeding. Try to keep some larger plants such as ferns and anubias. When given adequate swimming space and plants you can expect these fish to patrol around the tank in their school, providing a nice, organized look in the tank.

Diet & Feeding

There is nothing too special to note about their diet. They are quick to respond to feeding and do well on standard flake foods/prepared foods. They will also enjoy any live or frozen foods you provide them with, such as bloodworms and brine shrimp. Feeding live foods to schooling fish is always cool to see, so keep some on hand when you bring guests over. Normal floating foods will often see the school break apart into individual feeding.

Breeding & Sex Differences

The rasbora is easy enough to breed. They will often spawn in long, shallow tanks with big leaf plants. Keeping the water on the warmer side of their range, around 80 degrees, as well as feeding them live foods will accelerate the process. They spawn more frequently when they are under three years old.

Males can be seen as the more colorful of the fish. Additionally all rasbora have a small triangular spot on their sides. The females will have a more rounded spot while males will have a much sharper looking spot.

Mating can be observed as two fish swimming close to one another, with one of the two sometimes swimming upside down near the other fish. They will do this awhile before spawning. If you wish to raise the fry you will need to remove all adult fish from the tank or they will eat the fry before they can mature. Removing the eggs is also possible, but much more difficult as the eggs are very fragile.

Only a handful of eggs will grow into juvenile fish. This takes a week from the spawning day. You may see the larva swimming around the tank earlier, often under two days however you do not need to feed them until they are juveniles.

The larva will feed on their own egg sacs for the first 5 days, after which they will need to bed fed. This can be done using nauplii, which are freshwater copepods. Some people will say to feed them infusoria which is a more general term for single cell freshwater organisms.