At a glance the quick version
Looks how to spot one
Slender, active characin
A slim, streamlined tetra with such a vivid metallic blue sheen that many people first assume it has been artificially coloured. Females are fuller in the belly, and males show stronger colour, with a reddish tint on the anal fin when spawning.3
Personality what they are like
A busy, energetic fish that is generally peaceful. Kept in a decent-sized group, it saves its boisterous play for its own kind; it suits other active fish better than slow, long-finned ones.3
Daily activity how busy a day looks
Very active swimmer; needs a longer tank than its size suggests.3
Grooming and care the hands-on bits
Prefers soft to moderately hard, slightly acidic water and does not like alkaline conditions; keep water clean with regular changes.3
Home where they are happiest
A tank of at least 75 x 38 x 30 cm (about 86 litres) with open swimming room. Water 22-26 C, pH 5.5-7.0, hardness 5-12 dGH.3
Food basics what goes in the bowl
Omnivore. Offer small live and frozen foods such as bloodworm, Daphnia and brine shrimp, plus vegetable foods like spirulina flake or blanched spinach.3
Company who they like around
Keep at least 8-10 together. Good companions are other lively tetras, plecos and small catfish.3
The story where it all began
The blue tetra was formally described by German ichthyologist Axel Zarske in 2008. It is named after German aquarist Dieter Bork, who supplied the fish used for the description.21
Fun facts for the dinner table
- 1
Its colour is so intense that newcomers often think the fish has been dyed, but the blue is entirely natural.3
- 2
The species name borki honours aquarist Dieter Bork, who provided the type specimen.1
- 3
The genus name Knodus comes from a Greek word meaning knife or sword.1
- 4
Several different fish share the trade name 'blue tetra', so the scientific name is the safest way to identify this one.2
Recognised by the official bits
- IUCN Red List
- Assessed as Data Deficient (October 2022)1
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Blue Tetra. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- Knodus borki, FishBase fishbase.seused for distribution, IUCN status, author, etymology
- Knodus borki, Wikipedia en.wikipedia.orgused for distribution, size, history and naming
- Knodus borki, Seriously Fish seriouslyfish.comused for origin, size, appearance, tank and water parameters, diet, behaviour
Checked 2026-09-30. Text is written in our own words from these sources.