At a glance the quick version
Looks how to spot one
Tiny nano characin
A very small, slightly deep-bodied tetra whose whole body glows a ruby red in its home waters. Males stay a little smaller and carry the stronger colour, while females look rounder when carrying eggs. The red can look paler in aquarium fish.132
Personality what they are like
A gentle little shoaling fish that keeps to itself around other species. Males may claim small patches of the tank and posture at each other, which is part of their normal display.1
Daily activity how busy a day looks
Moderately active; spends its time shoaling and exploring among plants.1
Grooming and care the hands-on bits
Thrives in very soft, acidic, clean water; keep conditions stable with small regular water changes.12
Home where they are happiest
A tank with a footprint of at least 60 x 30 cm (about 54 litres), well planted with gentle flow. Water 20-28 C (FishBase gives 20-26 C), pH about 4.0-6.5 (up to 7.0 per FishBase), and soft water up to roughly 5-8 dGH.12
Food basics what goes in the bowl
A micropredator of tiny invertebrates. Offer fine dry foods along with small live or frozen foods such as baby brine shrimp, Daphnia and grindal worms.1
Company who they like around
Keep a group of at least 8-10. Best with other very small, calm species that suit the same soft, acidic water.1
The story where it all began
The ruby tetra was described by French ichthyologist Jacques Gery in the mid-1960s (sources give 1965 or 1966). Its names honour two people who helped collect the first specimens: publisher and aquarist Herbert R. Axelrod and fish exporter William Riese.32
Fun facts for the dinner table
- 1
At around 2 cm long, it is one of the smallest tetras kept in aquariums.1
- 2
The genus name honours Herbert R. Axelrod and the species name honours exporter William Riese, both involved in collecting the type specimen.2
- 3
Rival males set up tiny territories inside the shoal and show off to each other.1
- 4
It is less often seen in shops than its relatives, probably because its natural range is remote and small.1
Recognised by the official bits
- IUCN Red List
- Assessed as Least Concern (March 2021)2
- FishBase
- Listed as of commercial interest in the aquarium trade2
The care rhythm a typical week and year
A typical home-care rhythm for a Ruby 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 Ruby Tetra?
Feed your Ruby Tetra small amounts once or twice daily. Offer fine dry foods along with tiny live or frozen foods like baby brine shrimp and Daphnia. Furry Diary's starting plan suggests daily small meals.1 Pet Wiki plan
What does a Ruby Tetra eat, and what should it never eat?
Ruby Tetras are micropredators that eat tiny invertebrates. They enjoy fine dry foods and small live or frozen foods such as baby brine shrimp, Daphnia, and grindal worms. There is no specific list of foods to avoid, but always offer appropriately sized items and ask a vet if unsure.1
How much space does a Ruby Tetra need?
A Ruby Tetra needs a tank with a footprint of at least 60 x 30 cm, which is about 54 litres. This gives them enough space to shoal and explore among plants.1
What temperature, light or water does a Ruby Tetra need?
Ruby Tetras need soft, acidic water with a temperature between 20-28°C (ideally 20-26°C per FishBase), pH around 4.0-6.5 (up to 7.0), and very soft water up to roughly 5-8 dGH. They thrive in clean, stable conditions with gentle flow and plenty of plants. Lighting is not specified, but moderate levels typical for planted tanks work well.12
How often should I clean a Ruby Tetra's home?
Clean your Ruby Tetra's home with a 25% water change every week, along with glass cleaning. Rinse the filter in old tank water monthly, never tap water. Furry Diary's starting plan suggests these weekly and monthly tasks to keep water stable. Pet Wiki plan
Can a Ruby Tetra live with others?
Yes, Ruby Tetras are gentle shoaling fish that do best in a group of at least 8-10. They can live with other very small, calm species that enjoy the same soft, acidic water. Avoid larger or boisterous tankmates.1
How long does a Ruby Tetra live?
The lifespan of a Ruby Tetra is not specified in the available information. It varies depending on care and genetics, so ask a good breeder or an exotic-pet vet for a typical range.
Can I handle a Ruby Tetra?
Handling a Ruby Tetra is not covered in the provided facts. As a delicate nano fish, it is best to avoid handling; consult a vet or experienced aquarist if needed.
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.
- Axelrodia riesei, Seriously Fish seriouslyfish.comused for origin, size, tank and water parameters, diet, behaviour, appearance
- Axelrodia riesei, FishBase fishbase.seused for distribution, length, water parameters, IUCN status, etymology
- Ruby tetra, Wikipedia en.wikipedia.orgused for range, length, colour, history and naming
Checked 2026-09-30. Text is written in our own words from these sources.