Tiger knifefish, Gymnotus tigre

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Matt Clarke looks at the stunning Tiger knifefish, or Macana tigre, a beautiful gymnotid knifefish from South America.

Common name: Tiger knifefish, Macana tigre

Scientific name: Gymnotus tigre

Origin: Mainly Colombia. The type specimen was collected in the Amazon at Letitia, but it's also found in the Amazon in Peru and Brazil, in the Rio Tapajos in Brazil and from Ecuador's Rio Pastaza.

Size: Museum records state an adult size of 40cm/16" for G. tigre, but this adult was probably more like 45cm/18".

Diet: Fish and invertebrates.

Aquarium: These electrical fishes are adapted for life in very dark peaty waters which don't even get much light during the day, so make sure the tank is very shady. Furnish the tank with bogwood and use a silver sand substrate. Males of the larger gymnotids can sometimes be aggressive, so be careful about mixing this with similar fish. Robust but placid cichlids, such as Heros, Acarichthys or Geophagus, should be safe tankmates. Given the large adult size, a tank of at least 120cm/4' is required for this fish, preferably much larger.

Breeding: Little is known about Gymnotus. Males of at least two other species in this genus construct and guard floating nests made from aquatic plants and foam, and G. carapo is a mouthbrooder.

Notes: This is quite a recent discovery. It was only described in 2003 by Albert and Crampton along with six other Gymnotus species. This one is a member of the Gymnotus carapo group.

Similar species: There are 26 Gymnotus species, with six in the carapo group: carapo; choco; esmeraldas; henni; paraguensis and tigre.

Identification: According to Albert and and Crampton, the world's experts on the Gymnotidae, there should be a series of pale, yellow bars on the flanks "with high contrast margins which are as broad or broader than brown bands anteriorly". The chin, operculum and under the eyes, should have irregular pale yellow blotches, and the tail end should have a series of oblique hyaline (transparent) and dark stripes on the back end of the anal fin. There should be also 190-240 branched rays in the anal fin, not that you'd be able to count 'em, though...

Availability: This fish was imported from Colombia by Tom Halvorsen Ltd and was the only one in the shipment. It's extremely rare in the trade.

Price: About 200-300 for one like this.