The Harlequin Rasbora, a fascinating little fish belongs to the family Cyprinidae. It comes from the Malay Peninsula, Thailand and Sumatra. This, the most common and easy to keep of the Rasbora family, was first imported into Europe in 1906. Later, making its way to the rest of the world’s aquariums very soon after.
The water in the Harlequin Rasbora’s natural setting is extremely soft and its temperature often rises quite high during the day, while dropping much lower at night.
Now-a-days, most of these colorful little fish have been raised on Florida tropical fish farms and in aquariums so their natural need for very soft water has been somewhat abided.
The appearance of the Harlequin Rasbora, with a dark triangular patch extending back from the base of the caudal fin, is very distinctive. The silvery tone of the rest of the body may be broken with yellow or reddish markings, which has resulted in this species also becoming known as the Red Razor.
Males tend to be brighter in color than females and have slimmer bodies. The female has a rounder lower profile and at breeding time become quite plump. Another way of sexing the Harlequin Rasbora is even simpler. Male and female are roughly the same size, but the sexes are easily distinguished. Males are much redder in the dorsal and tail fins, also in the caudal peduncle region. The female is more golden, and when full of roe her belly is deeper than that of her mate.
It is surprising that so many aquarists and so many information sources are under the impression that the fish are unsexable. Bottom line, the males are always redder, at breeding time the females are always broader and fatter, and it becomes quite obvious when you get the hang of it!
In nature, the Harlequin Rasbora does not usually tolerate contact with fish of other species, so if they are to be kept in a community tank, they should be kept in odd numbers of 5-7 or more, and given rocks and privacy places, with this in place they will be happy community members, and never bother or interfere, in any way, with other fish in the tank.
Special Note: Shoal fish should always be kept in odd numbers of 3-5-7 or more because this insures that there will be odd numbers of males and females. This encourages competition and interest among the shoal of like species fish, keeping them together, rather than pairing them off in different areas of the aquarium.
Note on Breeding the Harlequin Rasbora: This fish, if in a well planted aquarium, with other docile community fish has been known to actually breed, their eggs hatch, and the young grow to various stages of maturity right in the community aquarium with little or no assistance from the aquarist. This is indeed a fun fish to breed and very willing to give a beginner very satisfying results!
Set up the breeding tank in the usual way for the Cyprinidae, but for plants, Cryptocoryne should be used, since this species likes to lay its eggs on the underside of broad leafed plants, and the Cryptocoryne is their plant of choice in their natural environment, increased percentages remember?
Note on Set-up: Always increase the percentages of successful breeding by matching as much of a fishes natural environment as possible, both in water condition and in props such as plants, rocks and time of day simulation
Since the advent of air travel Harlequin Rasbora’s have been imported by the 10s of thousands from their native land of Malaya. They are shipped 500 to a 1 foot by 1 foot by 1 foot boxed plastic bag filled with pure oxygen and 1 ½ gallon of their natural water. Few die and so they are always in demand. Inspite of the constant demand, the source of supply in their natural home is never depleted. They literally swarm in great numbers in pools in Malaya, then all are caught in a net, the pool fills again in what seems like weeks! The trick is to make the tank like a pool in Malaya!
First, place a well-conditioned adult male with a younger heavy with roe female in the breeding tank late in the day. Courtship should probably begin early the next morning and is instigated by the male and includes the usual fin-flaring and dancing in front of his mate.
The pair starts swimming around the tank together and eventually moves under a suitable broad leaf of a plant. Here they turn upside down and deposit a few eggs. Then they move off and court some more before coming back to spawn again, which will probably take place on the same plant, or even the same leaf.
Occasionally they deposit eggs on a fine leaf plant, but this is rare, they look for a wide leaf. When healthy pair is finished they will have deposited 25-100 eggs and go placid. The Harlequin Rasbora is not an avid egg eater, but they will eat some of the eggs occasionally, since the batch of eggs are relatively few in number compared to others species we have discussed, every egg is precocious, therefore remove the parents as soon as breeding is concluded.
The fry hatch in about 24 hours, and the fry are free swimming on the third day. At this point they should be fed infusoria or liquid fry food or an egg yolk squeezed through a cheese cloth for the first week. Then wean them slowly onto baby brine shrimp and commercial dry ground fry food. They grow extremely fast and are a pretty good size within three months if fed well and often. Add a sponge filter after the first week, and change 10% of the water every week after the first month.
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