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i have had a school of black teras(black widows) since i got my tank.
i saw a long-fin black tetra all by himself so i bought him.
i was just wondering if anyone knows how they get their long fins.

They're specifically bred to be that way. It's like the different types of dogs and cats- fish of a certain species can have numerous variations, some of which (like the long-finned black skirt tetra) are human-encouraged.

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

Black Widow Tetras, Gymnocorymbus ternetzi, have been domesticated for so long (Innes reported their breeding in the first edition of his venerable book back in the late 1930s!) that they've been subject to selective breeding to produce different strains, the Long-Finned Black Widow being one such strain. There's also a "White Widow" (not a true albino - it doesn't have red pupils and there are still some black markings on it) that has much of the black colouration missing (however, it's still capable of producing melanin), and there's a true albino strain in existence, though this is MUCH rarer than the "White Widow".

If you check your aqurium textbooks, you'll also find that this fish has been given an unusually large number of common names: among the ones I've encountered are Black Widow, Black Skirt, Petticoat Tetra, Butterfly Tetra and Blackamoor. Rather than muck about with different colour schemes, I'd prefer it if someone figured out a way of making these fishes retain their juvenile intensity through adulthood - juveniles can be wonderful to look at, but adults become more washed out with age. Quite why this is puzzles me, because there are several fishes that, if anything, become even more beautiful with age, such as the Rainbow Fishes and numerous Cichlids ...


Panda Catfish fan and keeper/breeder since Christmas 2002

Like Sirbooks said it's a trait that was bred into the fish.

Good work on buying the lone widow and adding her to your school Black Widows dont school tightly but they love being in a group