Fire Ant Tetra is a striking, nano-sized South American tetra that has rapidly become popular in the hobby due to its intense red–orange coloration, small adult size, and peaceful schooling behavior. Originally a rare import, it is now reliably available thanks to successful captive breeding, including lines distributed by Aquarium Glaser. 

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Species Overview

• Scientific name: Hyphessobrycon myrmex
• Common name: Fire Ant Tetra
• Maximum size: ~2.5–3 cm (about 1–1.2") 
• Origin: Brazil – Rio Formiga, a tributary of the Rio Juruena (upper Rio Tapajós basin, Mato Grosso) 
• Discovery: Scientifically described in 2017, making it a very recent addition to aquariums 

The species name myrmex means “ant” in Greek, referencing both its tiny size and the Rio Formiga (“Ant River”) where it was discovered. 

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Appearance & Sexual Dimorphism

• Males: Brilliant red to fiery orange body, most intense in dominant (alpha) males 
• Females & juveniles: Pale yellow to greenish, lacking red coloration 
• Markings: Dark lateral stripe along the body; clear dorsal fin; red accents on belly and anal fin
• Body form: Slender, laterally compressed “classic tetra” shape 

This dramatic color contrast between sexes (sexual dichromatism) makes the species especially attractive in groups.

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Behavior & Temperament

• Temperament: Peaceful, shy, and schooling
• Activity level: Active mid–lower water swimmer
• Social needs: Best kept in groups of 8–10+ to reduce stress and enhance coloration 

They are ideal for community and nano aquariums, provided tankmates are equally small and non-aggressive.

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Aquarium Care Requirements

Tank size

• Minimum 10–15 gallons for a proper school; larger tanks improve confidence and color 

Water parameters

• Temperature: 22–28 °C (72–82 °F) 
• pH: 6.0–7.5 (slightly acidic to neutral) 
• Hardness: Soft to moderately hard water

Aquascaping

• Sandy or fine gravel substrate
• Dense planting, driftwood, leaf litter
• Floating plants to diffuse light and mimic natural conditions 

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Diet

• Omnivorous micropredator
• Accepts:
  • High-quality micro pellets or flakes
  • Frozen foods (daphnia, cyclops, baby brine shrimp)
  • Occasional live foods for conditioning 

A varied diet significantly improves male coloration.

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Breeding Notes

• Captive breeding: Now well established (including Aquarium Glaser-bred stock) 
• Breeding difficulty: Moderate to easy
• Soft, slightly acidic water and fine-leaved plants or spawning mops are recommended
• Remove adults after spawning, as eggs are not guarded

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 Ideal Tankmates

• Other small tetras
• Rasboras
• Corydoras (dwarf species)
• Otocinclus

Avoid large or aggressive fish that may intimidate or prey on them.

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