Product Details

Kerri Tetra – Inpaichthys kerri

The Kerri Tetra is a small, elegant South American tetra with a blue, purple or royal sheen and peaceful shoaling behaviour. Correctly named Inpaichthys kerri, it is often sold as the Royal Tetra, Blue Emperor Tetra or Purple Emperor Tetra. This is a colourful community fish for mature planted aquariums, where a group can show its best colour, confidence and natural social behaviour.

Key Identification:

Common Name: Kerri Tetra
Other Names: Royal Tetra, Blue Emperor Tetra, Purple Emperor Tetra, Blue Kerri Tetra, Emperor Tetra Kerri
Scientific Name: Inpaichthys kerri
Incorrect / Trade Spelling: Impaichthys kerri
Fish Type: Tetra / Characin
Water Type: Freshwater

Natural Range & Habitat:

Inpaichthys kerri is native to Brazil, where it is recorded from the Aripuanã River in the upper Madeira River basin, Mato Grosso. This is a South American freshwater tetra from tropical river drainage habitats.

In the aquarium, Kerri Tetras do best in mature planted setups with clean water, shaded areas, open swimming space and gentle to moderate flow. Wood, leaf litter, darker décor and floating plants can help create a more natural, secure environment and bring out their blue-purple tones.

Appearance & Adult Size:

Kerri Tetras have a slim tetra body with a metallic blue, violet or purple sheen along the flanks. Depending on sex, mood and lighting, the body can appear steel-blue, lavender, royal blue or purple. The fins are usually clear to lightly coloured, and mature males often become slimmer and more strongly coloured than females.

A useful sexing feature is the adipose fin colour: males usually show a blue adipose fin, while females often have a red-orange adipose fin. Adults usually reach around 3–4 cm in aquariums, making them small but visible community fish.

Aquarium Suitability:

This species is well suited to peaceful planted community aquariums, South American-style displays and mixed tetra setups. It is hardy once settled, but should still be added only to a mature, fully cycled aquarium with stable water quality.

Kerri Tetras are not suitable for aggressive communities, large predators, very hard-water livebearer setups, tiny unfiltered tanks or aquariums with boisterous fish that may outcompete or stress them.

Recommended Aquarium Size:

A practical minimum is 60 litres for a small group, with a tank length of at least 60 cm recommended. Larger aquariums of 75–90 litres or more are preferred for bigger shoals and mixed communities.

Keep in a group of at least 6, with 8–10 or more preferred. Larger groups are more confident, show better colour and reduce minor chasing between individuals.

Water Conditions:

Temperature: 23–27°C
pH: 5.5–7.0
Hardness: Soft to moderately hard; soft, slightly acidic water preferred
Additional Notes: Kerri Tetras show best colour in stable, clean water with subdued lighting and plant cover. Avoid sudden changes in pH or hardness. They can be adaptable once settled, but they should not be kept long term in very hard, alkaline conditions.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Kerri Tetras are peaceful community fish, although males may display and chase lightly within the group. Suitable tank mates include other peaceful tetras, rasboras, pencilfish, small Cory-type catfish, Otocinclus, dwarf cichlids with care, small peaceful plecs and calm community fish that enjoy similar water conditions.

Avoid large predators, aggressive cichlids, very boisterous barbs, fin-nipping species and extremely shy nano fish that may be intimidated by active tetras. They should not be kept singly or in pairs, as group life is important for confidence and natural behaviour.

Feeding:

Kerri Tetras are easy-feeding omnivores. Offer quality fine flakes, micro pellets or small soft granules as the staple diet. Supplement with frozen or live foods such as daphnia, cyclops, brineshrimp, mosquito larvae and small bloodworm.

A varied diet helps maintain colour, condition and breeding readiness. Feed small portions that are eaten quickly, as they are active midwater feeders.

Behaviour in the Aquarium:

This species usually swims in the middle levels of the aquarium, moving in a loose group through plants and open water. Males may display to rivals and females, especially once settled, showing stronger blue-purple colour under good lighting.

Kerri Tetras are egg scatterers and do not provide parental care. If spawning occurs in a community aquarium, eggs and fry are usually eaten unless a separate breeding setup is used.

Care Notes:

Add Kerri Tetras only to a mature, fully cycled aquarium. Provide plant cover, shaded areas and open swimming space. Maintain stable water quality with regular partial water changes, and avoid rough tank mates that may outcompete them.

This species can look subdued in shop tanks or bright bare aquariums, but colour usually improves once settled into a planted aquarium with a proper group and calm surroundings.

Recommended For:

Beginner to intermediate

Availability:

Occasional / Usually captive-bred or farmed, with imports also seen

Image Disclaimer:

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Natural variation in size, blue-purple sheen, fin colour, body tone and markings can occur between individual fish.