Why are my Red Eye Tetras nipping the fins of other fish?

Fin-nipping in Red Eye Tetras is usually a sign of stress or boredom caused by being kept in a group that is too small. Increasing their shoal size to at least 6 to 8 individuals typically curbs this behaviour, as they will bicker harmlessly among themselves instead.

Are Red Eye Tetras suitable for a planted aquarium?

Yes, they are highly suitable. They do not eat healthy aquatic plants and their silver bodies look magnificent against a backdrop of dense green foliage. Furthermore, plants provide the shelter they instinctively crave.

How many Red Eye Tetras should I keep together?

You should keep an absolute minimum of 6, though a shoal of 8 to 12 or more is much better. Larger groups display more natural schooling behaviours, better colouration, and a calmer temperament.

Can I keep Red Eye Tetras with a Betta?

It is not recommended. Bettas are slow-moving and have long, trailing fins, which present an irresistible target for a curious or boisterous Red Eye Tetra.

FreshwaterTropicalBeginner

Red Eye Tetra

Moenkhausia sanctaefilomenae

A remarkably hardy and energetic schooling fish, renowned for its bright red eyes and striking black-and-yellow tail bands.

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Ideal Conditions

Temperature: 22 – 26 °C
pH range: 6 – 7.5
Hardness: 2 – 15 dGH
Adult size: 5 – 7 cm
80L for a basic shoal, 120L+ for larger groups: 80 litres+
Lifespan: 3 – 5 years
Diet: Omnivorous
Water flow: moderate
Preferred setup: Planted with open swimming spaces

About the Red Eye Tetra

The Red Eye Tetra is a long-standing favourite in the aquarium hobby, prized for its durability and striking metallic appearance. With a deep-bodied, silvery profile offset by a bright splash of red above the eye and a distinctive tri-colour tail root, a large school creates a captivating display. They are highly active fish that bring movement and life to the mid-water regions of the aquarium.

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Is it right for your tank?

Check Red Eye Tetra against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Red Eye Tetra comes from

Native range

Paraná River Basin, Paraguay River Basin, Uruguay River Basin, Parnaíba River Basin

Countries / regions

Brazil, Paraguay, Argentina, Peru

Habitat

Clear, slow-moving rivers, flooded forests, and heavily vegetated tributaries.

Widely distributed across central and eastern South America.

Similar species

Black Skirt Tetra
Gymnocorymbus ternetzi
Buenos Aires Tetra
Hyphessobrycon anisitsi
Blind Cave Tetra
Astyanax mexicanus

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Bronze Corydoras
Corydoras aeneus
Peaceful bottom dwellers that occupy a different zone of the aquarium and will not interact negatively with the tetras.
Great
Bristlenose Pleco
Ancistrus sp.
Robust and peaceful algae eaters that happily co-exist with active mid-water shoaling fish.
Great
Harlequin Rasbora
Trigonostigma heteromorpha
Similarly sized, active schooling fish that enjoy the same water parameters.
Great
Angelfish
Pterophyllum scalare
Red Eye Tetras can sometimes be fin-nippers, which poses a risk to the trailing fins of Angelfish, whilst fully grown Angels may eat very young tetras.
Compatible with caution
Siamese Fighting Fish
Betta splendens
The long, flowing fins and slow movement of a Betta make it a prime target for nipping by boisterous tetras.
Not recommended
Fancy Guppy
Poecilia reticulata
Male guppies have delicate, trailing tails that are easily damaged by the nippy behaviour of Red Eye Tetras.
Not recommended

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