Gymnocorymbus ternetzi, Boulenger, 1895
Origin: Brazil;Rio Paraguay, Rio Guapore, Rio Amazonas, Rio Negro, Rio Pilcomayo, Rio Beni, Rio Madeira, Rio Tapajos and lake Rogoa. Bolivia; Rio Mamore,Paraguay; Rio Paraguay.
Etymology: Gymnocorymbus L.: with naked head. ternetzi L.: Named after Ternetz(?)
Synonyms:Tetragonopterus ternetzi, Moenkhausia ternetzi
First European import: 1935, from the USA, where the fish were first imported in 1934.
Description:See picture, older animals turn greyish, but juveniles have deep black dorsal and anal fins.
Care: Really easy to keep fish, suitable for every community tank. Very good beginner fish that have no particular requirements to waterquality or environment. They shouldn't be kept in a small tank, minimum 60 cm but better is a 80 cm or larger community tank, with plants around the sides and in the back and a large swimming space in the front and in the middle. Dark soil and some shadow bring out the colors a bit better. Temperatures between 20 and 23 degrees, although higher temperatures are also accepted.
Feeding:All food is taken, can be kept and bred on a flake food diet.
Breeding: Gymnocorymbus ternetzi will spawn in schools between plants. No need to raise the watertemperature, although higher temps(25-28) will increase the chance for succes. Usually spawning will take place in schools between plants where the eggs are deposited. After 8 days the fish may spawn again. In nature they will spawn between december and february, although in aquariums they can spawn the whole year round. The fry can immediately master relatively large chunks of food, and grow quite fast if the water is changed often enough.
Sexual dimorphism:Males are smaller than the females, and also thinner. Besides that the males may have white spots in the caudal fin, which are lacking in the female.
Prices: Netherlands: 0.75-1.20€
Additional: Gymnocorymbus ternetzi can reach the respectable age of 10 years and older! The fish inhabit a large area in South-America, but the exact distribution has still to be determined. The fish do occur in the Rio Paraguay, which originates in Brazil, and have been reported from Paraguay. If the fish actually occur(Or have occurred before pollution)as far south in the river as reported has to be researched.
An albino and a form with elongated fins exist.
Picture references:All pictures : E. Naus.
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