Red Moenkhausia - Rubra Tetra - Moenkhausia Rubra

Red Moenkhausia / Rubra Tetra | A Rare and Iridescent South American Gem

The Rubra Tetra (Moenkhausia rubra) is a genuinely stunning and relatively rare tetra that deserves far more attention in the freshwater aquarium hobby than it currently receives. Also known as the Blue Sapphire Tetra — a name that hints at its dual personality — this captivating little fish combines two striking visual elements in one compact package: a warm reddish-orange flush across the back of the body, most intense on breeding males, and a shimmering blue-green iridescence that catches the light and shifts with every movement. The name "rubra" comes from the Latin word for red, a nod to the warm body tones that give this species its distinctive look.

In a well-planted tank under good lighting, a school of Rubra Tetras is a genuinely eye-catching display — constantly shifting between warm red and cool blue-green as they move through the water together.

Rubra Tetra Care Guide

Care at a Glance

• Scientific name: Moenkhausia rubra
• Also known as: Rubra Tetra, Blue Sapphire Tetra, Red Moenkhausia
• Adult size: up to 2 inches (5 cm)
• Minimum tank size: 20 gallons — longer tanks preferred for schooling behaviour
• Temperature: 76–82°F (24–28°C)
• pH: 6.0–7.2 — soft to moderately hard water preferred
• Best kept in groups of 8 or more
• Lifespan: 3–5 years with good care

Rubra Tetra Tank Setup

A well-planted aquarium with dark substrate, open central swimming space, and gentle to moderate water flow suits Rubra Tetras perfectly. Dense planting along the sides and background provides security and helps these fish feel confident enough to school actively and display their best colouration. Subdued lighting with floating plants to diffuse intensity brings out both the warm red tones and the blue-green iridescence simultaneously — the contrast is particularly striking against dark hardscape and planting.

Feeding Your Rubra Tetras

Omnivorous micropredators that are easy and unfussy to feed. A high quality micro flake or small pellet makes an excellent staple diet, supplemented regularly with frozen or live foods such as baby brine shrimp, daphnia, cyclops, and bloodworm. A varied, protein-rich diet will enhance the reddish colouration of males and keep the whole school in top condition.

How Many Rubra Tetras Should You Keep?

As a true schooling species, Rubra Tetras should be kept in groups of 8 or more. In a proper school they are active, confident, and display their best colouration — particularly the males, who intensify their red tones when competing for female attention. Small groups tend to be more timid and less visually impressive.

Rubra Tetra Tank Mates

• Other small, peaceful South American tetras and rasboras
• Corydoras and small peaceful bottom dwellers
• Dwarf cichlids such as Apistogramma and German Blue Rams
• Peaceful gouramis and small danios
• Shrimp — generally safe with adults, use caution with very small juvenile shrimp
• Avoid large or aggressive fish and fin-nipping species