Among the most important ornamental fishes are the species of Harlequin barbs. Formerly they were addet to the catch-all genus Rasbora, but nowadays it is everywhere accepted that they belong to a genus on their own named Trigonostigma. There are four described species and one of unclear status. Four of them are regularly stocked by us and because they continously become confused, we will take the opportunity to show you the differences.
1. The real Harlequin barb, Trigonostigma heteromorpha
This species has the largest trinagel-spot of all species. The spot covers almost completely the hinder half of the body. Nowadays almost all specimens available in the trade are bred ones, but now and then we can also offer wild collected ones like the specimen depicted.
2. The Purple Harlequin barb, Trigonostigma espei
This species is sometimes also called “Elongated Harlequin barb”. It can be recognized by the size of its triangle spot that covers only the lower half of the hinder half of the body. The gap between the operculum border and the triangle spot as well as the back above the triangle spot is brillantly coloured with a deep purple red.
3. The Orange Harlequin barb, Trigonostigma cf. espei
This fish fits perfectly to T. espei with the exception of the basic colour which is a bright orange instead of a deep purple. This leads to much confusion with the following species (T. hengeli). Especially subadults can be confused easily. However, adults can be distinguished for sure by the colour of the gap between the border of the operculum and the triangle spot, which is a bright orange in T. cf. espei and white in T. hengeli.
4. The Small Harlequin barb, Trigonostigma hengeli
This Harlequin barb is the tiniest of all. The triangle spot is relative small and bordered by a bright orange line. The gap between the border of the operculum is whitish as well as the back above the triangle spot.
All four Harlequin barbs are wonderful aquarium inhabitants which develop fantastic colours when kept in soft and acidic black water. None of them becomes larger than 4 cm, in the wild they are usually much smaller.
Text and photos: Frank Schäfer
