Green Neon Tetra

Paracheirodon simulans

Also known as: Green neon, Simulans tetra

Water Parameters

• Temperature: 24–29°C
• pH: 4–6.5
• Hardness (GH): 18–89 ppm (1–5 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

The smallest and arguably the most uniformly luminous of the blue-line tetras: where the neon and cardinal carry a band of red, the green neon is almost pure shimmering blue-green from nose to tail, and a tight school under low light over dark substrate is one of the quieter showpieces of nano keeping. The trade-off is that it is the fussiest of the three about water, needing genuinely soft, acidic, warm, blackwater-style conditions and a mature tank to do well long-term. Most are wild-caught and arrive sensitive, so they should never go into a new tank. In the hard tap water of much of Australia they need softening to thrive rather than merely survive, which makes them an intermediate fish despite their beginner looks. Given the right water and numbers, exceptional value as a living shimmer. Being the fussiest of the three, it wants a very low carbonate hardness (KH), well under 4 dKH (about 70 ppm), to go with that acidic blackwater; hard, high-KH water is unsuitable and prevents breeding.

Tankmates

Even smaller than the neon tetra and more demanding of soft, acidic, warm water, the green neon is a true nano schooler that must be kept in a group of eight or more, ideally a dozen, to shoal tightly and show its iridescent blue-green stripe. Peaceful and too small to threaten any tankmate, including adult shrimp, but also small enough to be eaten by anything larger, so keep it strictly with other nano species. It comes from blackwater habitats and shows the least tolerance of the three blue-line tetras for hard, alkaline water, so it is a poor match for hard Australian tap supplies without softening (rainwater or RO). Best in a mature, planted, dimly-lit blackwater nano tank.

Compatible with

• Cardinal Tetra
• Ember Tetra
• Chili Rasbora
• Harlequin Rasbora
• Pygmy Corydoras
• Otocinclus
• Cherry Shrimp

Avoid keeping with

• Betta
• Angelfish
• Large Cichlids
• Fin Nippers

Common Problems

• poor health and colour in hard, alkaline water
• sensitivity as wild-caught fish in new tanks
• stress in groups smaller than 8
• sensitivity to parameter swings

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20