The short answer
A 10 litre tank is a true nano and honestly too small for most fish. The realistic options are a colony of dwarf shrimp, a few snails, or at most a single betta if the tank is heated, filtered and lidded. There is no room for a school here, so think invertebrates first and fish a distant second.
Why 10 litres is so limiting
The old “one inch of fish per gallon” rule is useless and dangerous, especially at this size. It ignores adult size, waste output (bioload), whether a fish schools, its temperament, and how strong your filtration is. In just 10 litres, water parameters swing fast: a small overfeed or a missed water change can spike ammonia within hours. That is why understocking is not optional here — it is survival.
What actually works in 10 litres
- A dwarf shrimp colony — cherry shrimp are the classic choice: colourful, active and low-waste
- 1 betta — a betta can live here with gentle flow, though it prefers more space
- A few nerite or ramshorn snails as quiet cleanup
- A shrimp-and-snail tank with no fish at all — a beautiful, stable option
Avoid every schooling fish (neon tetras, rasboras, danios) and anything sold as “nano” that still needs a group. Six is the minimum for a school, and six fish do not belong in 10 litres.
Before you add anything
Whatever you keep, cycle the tank first so the filter can process waste, then stock slowly and feed sparingly. Keep up small weekly water changes. If you want real fish, the next size up opens far more doors — see how many fish in a 30 litre tank and our best nano aquariums guide.