The short answer
Keep neon tetras in a group of at least 6, and ideally 8–12. Neons are schooling fish, so bigger groups keep them calm, colourful and confident. A small huddle of two or three leaves them stressed and washed-out. Give a school of 8–12 around 40–60 litres of warm, gently filtered water and they’ll shoal beautifully.
Why the group size matters
In the wild neon tetras live in large shoals, and safety in numbers is wired into their behaviour. In too small a group they feel exposed and spend their time hiding, their colours fade, and stress makes them prone to illness. A proper school spreads out the attention of any tankmates and encourages the tight, flickering swimming that makes neons worth keeping.
Giving the school what it needs
Neons thrive with:
- Numbers — 8 to 12 or more where space allows
- Space to shoal — length matters more than height
- Planted cover and subdued lighting to bring out their colour
- Peaceful tankmates — avoid fin-nippers and anything large enough to eat them
They are sensitive to unstable water, so mature, well-filtered tanks suit them best. Add the whole school over a couple of batches rather than all at once.
Before you add them
Only add neons to a fully cycled aquarium, and acclimate them slowly as they dislike sudden changes. Keep up regular water changes for steady parameters. For stocking limits by tank size, see how many fish in a 40 litre tank, and for another popular schooler read how many corydoras to keep together.