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 a typical week and year
A typical home-care rhythm for a Blue Tetra. A starting point, not a vet's advice.
- 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
Owner questions the things everyone asks
How often should I feed my Blue Tetra?
Feed your Blue Tetra small amounts once or twice a day. Furry Diary's starting plan suggests feeding daily, and you can adjust based on how much they eat in a couple of minutes.3 Pet Wiki plan
What does a Blue Tetra eat, and what should it never eat?
Blue Tetras are omnivores and enjoy small live or frozen foods like bloodworm, Daphnia, and brine shrimp, plus vegetable foods such as spirulina flake or blanched spinach. Avoid feeding anything that could foul the water or is not suitable for small fish; always check with a vet or good breeder for specific foods to avoid.3
How much space does a Blue Tetra need?
A Blue Tetra needs a tank of at least 75 x 38 x 30 cm (about 86 litres) with open swimming room. They are very active swimmers, so a longer tank is better than a tall one.3
What temperature, light or water does a Blue Tetra need?
Keep the water at 22-26°C with a pH of 5.5-7.0 and hardness of 5-12 dGH. They prefer soft to moderately hard, slightly acidic water and do not like alkaline conditions. Provide gentle lighting and regular water changes to keep conditions stable.3
How often should I clean a Blue Tetra's home?
Furry Diary's starting plan suggests a weekly 25% water change, weekly glass cleaning, and a monthly filter rinse using old tank water (never tap water). Regular cleaning keeps the water healthy for your fish. Pet Wiki plan
Can a Blue Tetra live with others?
Yes, Blue Tetras are peaceful and do best in a group of at least 8-10 of their own kind. Good companions include other lively tetras, plecos, and small catfish, but avoid slow, long-finned fish.3
How long does a Blue Tetra live?
Lifespan varies depending on care and environment. For specific information, ask a good breeder or an exotic-pet vet.
Can I handle a Blue Tetra?
It's best not to handle Blue Tetras as they are delicate fish. Handling can stress them and damage their protective slime coat. Enjoy watching them swim in their tank instead.
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.
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Every fact on this page has a numbered source. Spotted an error? support@petwiki.app.
- 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.