The short answer
Nano fish are tiny shoalers built for small, planted tanks — think groups of little fish rather than one big one. The best include:
- Chili rasboras (among the smallest and most colourful)
- Ember tetras (warm orange, peaceful, hardy)
- Celestial pearl danios (CPDs — spotted, stunning)
- Endlers (small, active livebearers) and cherry shrimp
Keep a school, not a solo fish
Nano fish are shoaling species, so they need a group of at least six to feel secure and show their colours. That’s the opposite of picking one “pet” fish — the display is the movement of a little school. Because they’re so small, they suit tanks that would be far too cramped for standard community fish. Notably, neon tetras are a step too big and active for the smallest tanks; a group of chili rasboras or embers fits a 20-litre nano far better.
Give them a mature, planted nano
Nano fish look and feel best in a planted tank with gentle flow and plenty of cover. A mature, cycled aquarium is essential — small volumes are less forgiving of mistakes, so never rush the setup. A heater and a lid are worth having, and a gentle filter keeps the current soft for these delicate swimmers.
For stocking numbers, see how many fish in a 20 litre tank and how many fish you can keep. To choose the tank, see the best nano aquarium and browse the aquariums hub. A nano suits a planted setup too — see the best fish for a planted tank.