by Aaron Hunt

Created on: June 01, 2010

The Harlequin Rasbora (Rasbora heteromorpha) belongs to the Cyprinidae family.  It is native to the densely-planted backwaters of southeast Asia, including Thailand, Malaysia, and Sumatra.    Harlequin Rasboras are small fishes, often being approximately one inch long in retail environments and growing to 2 inches at full size.  It is an excellent community fish and does well in groups – preferably six or more.  They are very active and typically occupy the middle of the water column in the aquarium. 

The Harlequin Rasbora is a very attractive fish once acclimated, but it is often pale and washed out in appearance in the average dealer’s tank.  When properly acclimated, it has an oval body, pointed nose, and a slender tail.  The back half of the body has a triangular black wedge that leads to the tail.  The dorsal and caudal fins are garnet colored, as is the tail around the edges of the black wedge.  A heavily planted aquarium will show their optimal colors. 

They are very hardy and adapt to a wide range of water temperatures.  They will thrive at seventy eight degrees Fahrenheit, but can tolerate a range of sixty-eight to eighty-five degrees provided temperatures changes are made slowly.  They prefer neutral to slightly acidic water that is soft, but dechlorinated tap water is most likely sufficient in most areas.  

Like most rasboras, they are omnivorous eaters that will eagerly accept any offering.  Commercial fish food is a fine staple, but regular supplements of a frozen fish food and live invertebrates will keep them in top condition.  They seem to especially relish live blackworms. 

For breeding, a separate tank planted with broad-leaved Cryptocoryne plants is ideal.   Keep the males and females separated for two weeks prior to spawning and condition them on live foods.  Females are typically broader-bodied, while males are more slender.  Filter the breeding tank with a sponge filter.  Water conditions should be soft (less than six degrees general hardness), between eighty and eighty-two degrees, and filtered through peat.  The female will lay her eggs on the underside of the plant leaves.  Remove the spawning fish once eggs have been laid.  The eggs will hatch in approximately twenty-four hours.  They will be ready to feed on baby brine shrimp in four days.  The fist signs of the characteristic black wedge show at 14 days, and they will be an inch long in three months with regular water changes. 

The Harlequin Rasbora can easily live five years in the aquarium.  Their disposition, beauty, and size make them an ideal member of any tropical community tank.  They are hardy enough for beginners and provide a challenge to the experienced aquarist for spawning.   

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