Rasbora
(Rasbora heteromorpha)

Rasboras or Rasbora heteromorpha are members of the family Cyprinidae. Rasboras are native to Malaysia, Singapore, Sumatra, and southern Thailand. There are several species in the genus Rasbora. We will focus our attention on R. Heteromorpha. The Greek translation of Heteromorpha literally means differently shaped.

Rasboras are commonly referred to as harlequin fish or harlequin rasboras. This reference alludes to the black triangular patch on the back half of their bodies which is reminiscent to the patterns found on the costume of a harlequin.

Rasboras have a docile temperament. They make a good choice for a community tank provided their tank-mates are equally peace loving and not large enough to view them as a source of nutrition. Rasboras are shoaling fish. Shoaling fish are highly social creatures that function best as a community. They don’t adapt well to a solitary existence. It is recommended that you have at least four of these upper to mid tank swimmers in an aquarium.

Rasbora is a small fish. They only grow to an adult size of 1.5-1.75 inches. They thrive it soft, slightly acid water with a pH 0f 6.8 and a water temperature ranging between 74-78 °F. Under ideal conditions you can expect them to live up to 10 years of age.

Rasboras are omnivores. They will survive just fine on a diet of common tropical fish flakes.

Distinguishing sexes in rasbora is relatively easy. The male bodies are thinner. Females are more full bodied especially when carrying eggs. The distinct triangular marking on the rear of their bodies differs between sexes. The males have more defined angular markings that extend further back on the lower abdomen than the females.

In their natual habitat, they inhabit streams that are littered with jungle decay. As a result peat grows abundantly in the streams releasing humic acid into the water. These same conditions can be simulated by filtering the breeding tank’s water through peat or adding a thin layer of peat to the substrate. This will naturally increase the acid levels in the water. Make certain the peat contains no chemical additives or fertilizers.

A high protein diet of brine shrimp, tubifex or bloodworms will help induce the spawning cycle. Provide plenty of plant life to replicate their natural spawning grounds.

The male will begin chasing the male as a manner of courtship. Once the courtship phase is over the pair will spawn amid the foliage. Their eggs will be deposited on the underside of a broad leaf. Remove the adult from the breeding tank.

Once spawning has occurred you will want to darken the tank. The fry are susceptible to fungal growth. Surround the with paper or tin foil until the fry hatch and are free swimming. Eggs will hatch in about a day. After they hatch check the tank once a day. When you see the fry are free swimming it is time to start feeding them. This should take no longer than 3 days or so.

Free swimming fry can be fed liquid fry food formulated for egg layers or newly hatched brine shrimp. An economical and readily available alternative is powdered eggs. Make sure not to put too much in the water to avoid clouding it up.