Family: Characidae
A dazzling shoaling tetra with a neon-blue stripe and red tail — best kept in large groups.
A stripe of living neon over dark water — the tetra that sold the world on community aquaria. It needs soft, acidic water to show its best and a proper shoal to behave naturally.
Moderately easy, but with two non-negotiables: keep them in a school of 10+ (they color up and settle only in groups) and provide soft, acidic water (GH 1–2, pH 5.0–6.5). Kept singly or in hard water they stay pale and clamped.
Most likely neon tetra disease (Pleistophora), which bleaches the iridescent stripe gray-white. It's untreatable — remove affected fish immediately to protect the school. Plain stress from a new tank also fades color, but that recovers within 2–3 days of dim, quiet conditions.
Adults reach only 2.5 cm, but they're active schoolers — 60 L or more for 10–15 fish. Bigger tanks mean bolder, brighter fish; cramming 10 into 30 L causes chronic stress and losses.
Tiny mouths need tiny food: fine flakes or micro-pellets that float, plus occasional baby brine shrimp. They're poor competitors — with aggressive feeders they slowly starve no matter how much you add.
Peaceful tetras (cardinals, ember tetras), small corydoras and plecos. Avoid tiger barbs, serpae tetras and large cyprinids that nip fins or outcompete them. Note: cardinals grow larger than neons, so feed some sinking food so bottom dwellers aren't left out.
The neon (P. innesi) reaches 2.5 cm with a red stripe running only halfway and a shorter blue-green band. The cardinal (P. axelrodi) grows 3–4 cm, red running the full belly, deeper color, and roughly double the price. Care is nearly identical and they school together fine.
They come from Amazon blackwater creeks. In hard-tap regions, blend RO water 1:1 with tap, or use Indian almond leaves and peat to soften. Stability beats precision — anywhere in pH 5.5–7.0 held constant works; swinging between values is what kills them.
Three usual culprits: temperature swings over 2 °C during water changes, ammonia/nitrite spikes in immature tanks, and oxygen shortage at high density or high temperature. They tolerate cool water but not fluctuation — hold 20–26 °C steady.
Home breeding is genuinely hard and partly luck. It demands very soft acidic water (GH below 2), dim light, and live foods to condition the pair — plus prompt egg removal since parents eat them. Nearly all shop neons are hormone-bred commercially; buying juveniles is more practical.
Yes — moderate light keeps their color, but avoid harsh direct brightness. 6–8 hours daily over a planted tank is ideal; a dark background and subdued light make the blue-green stripe glow. Long-term darkness fades them.