10 kinds · tap one for a closer look
Active and can nip the fins of slow, long-finned fish.
342 species in our list are a good match.
Active and can nip the fins of slow, long-finned fish. Keep 6 or more to spread out any nipping.
Good to know: GloFish (the bright coloured kinds) are illegal to sell or keep in the EU.
Eats almost anything: flakes, pellets, frozen foods.
Tap a food to see what it is.
Males are slimmer and a little smaller than females.
Common problems. Tap one to see the signs. This is a guide, not a diagnosis.
Egg-scatterer · Easy
Easy to spawn in a separate tank; adhesive eggs are laid on fine-leaved plants and the adults eat the eggs if left in.
Buy 6 or more and let them pair up. Condition with live and frozen foods.
40 L tank with fine-leaved plants or mops, a spawning grate or marbles on the bottom, and dim light.
Warm water change with softer water and good feeding.
Eggs hatch in 18-36 hours and the fry swim freely a few days later; egg count not confirmed.
Feed infusoria or green water for days 1-3, then newly hatched brine shrimp and microworms. Keep light low early on. Grow out in a larger tank once fish are about 1 cm.
Described by Boulenger in 1895, a tough classic from the Paraguay and Guaporé basins. Fluorescent GloFish versions are genetically modified; they are sold in the United States but are illegal to sell or keep in the European Union.
George A. Boulenger of the British Museum described this tetra in 1895. It has been a staple of the hobby for decades thanks to its toughness. Long-finned, albino and pastel-dyed forms have been developed, along with genetically modified fluorescent strains.
First described by George A. Boulenger in 1895. Named for Named after Carl Ternetz, a Swiss naturalist who collected in South America.
16 facts checked with sources
Originally described as Tetragonopterus ternetzi Boulenger, 1895. Genus revised by Benine et al. 2015 (Zootaxa 3956) without changing this name.
FishBase: Gymnocorymbus ternetzi, Black tetraLegacy has no family. Subfamily Pristellinae. Melo et al. 2024 (Zool. J. Linn. Soc. 202(1), "Phylogenomics of Characidae") split the old Characidae; FishBase now places this species in Acestrorhamphidae (American tetras). Seriously Fish still says Characidae. Suggest showing 'Acestrorhamphidae (American tetras; formerly Characidae)'.
FishBase: Gymnocorymbus ternetzi, Black tetraBoth SL (standard length). FishBase (preferred for size) gives a maximum of 7.5 cm SL; Seriously Fish 6.0 cm SL, which matches the legacy 6 cm. 6 cm is a typical adult; 7.5 cm is the recorded maximum.
FishBase: Gymnocorymbus ternetzi, Black tetra · Seriously Fish: Gymnocorymbus ternetziSeriously Fish (preferred for husbandry) gives 6.0-7.0; FishBase is wider, 6.0-8.0, which would cover the legacy 7.5. Seriously Fish says captive-bred fish are unfussy about water chemistry.
Seriously Fish: Gymnocorymbus ternetzi · FishBase: Gymnocorymbus ternetzi, Black tetraLegacy has no hardness; sourced value recorded.
Seriously Fish: Gymnocorymbus ternetzi · FishBase: Gymnocorymbus ternetzi, Black tetra75 x 30 cm base x 30 cm height = 67.5 L; Seriously Fish rounds to 70 L. Legacy 80 L is more generous than the minimum.
Seriously Fish: Gymnocorymbus ternetzi · FishBase: Gymnocorymbus ternetzi, Black tetraSeriously Fish (preferred) recommends 12+, partly to spread out fin nipping; FishBase says 5+. Legacy 6 is below Seriously Fish.
Seriously Fish: Gymnocorymbus ternetzi · FishBase: Gymnocorymbus ternetzi, Black tetraLegacy "s" (semi-aggressive) overstates it: Seriously Fish calls it generally peaceful with a fin-nipping reputation that keeping a proper group usually solves. Keep a fin-nipper caution (traits.finNipper) so it is not matched with slow long-finned fish.
Seriously Fish: Gymnocorymbus ternetziSeriously Fish difficulty bar shows "Moderate", but the text recommends it for beginners.
Seriously Fish: Gymnocorymbus ternetziLegacy has no range field (its story names the basins correctly).
FishBase: Gymnocorymbus ternetzi, Black tetra · Seriously Fish: Gymnocorymbus ternetziLegacy also says males have a broader, longer anal fin; no source checked confirms that, so it was dropped.
Seriously Fish: Gymnocorymbus ternetziHatch time widened from legacy 24-36 h. Legacy "up to 500-1,000 eggs" was not found in Seriously Fish, FishBase or Wikipedia; left unconfirmed.
Seriously Fish: Gymnocorymbus ternetzi"Sold in many countries" is too broad: GloFish are banned in the EU (Swedish agency: buying and keeping them is prohibited, fines or up to two years prison). The GloFish black tetra appeared around 2012 (Wikipedia). Seriously Fish also warns that artificially dyed fish (not GloFish) are on sale and their lifespan is often shortened. Common names include black widow, butterfly and petticoat tetra; the leucistic form is sold as "white skirt".
FishBase: Gymnocorymbus ternetzi, Black tetra · Wikipedia: GloFish · Pet Scandinavia 4/23, "GloFish – på villovägar i Sverige" (quotes the Swedish Agency for Marine and Water Management)