Nano aquariums — roughly 20 to 60 litres — are hugely popular for shrimp, bettas and small shoaling fish, and they fit where a big tank never could. The catch is that smaller water volumes are less forgiving of mistakes, so choosing a good all-in-one nano tank with proper filtration matters more, not less. This UK guide covers the best options in 2026.
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Here are our picks.
- Nano aquariums (20–60 litres) suit shrimp, bettas and small shoaling fish.
- Smaller volumes are less forgiving, so choose the largest nano you have room for and cycle it fully.
- The Fluval Flex 57 is the best all-round nano; the Fluval Spec is ideal for a betta or shrimp.
- Avoid sub-20-litre 'betta cubes' — too small to stay stable.
A word on nano tank stability
Smaller volumes swing faster in temperature and water chemistry, so a nano tank is arguably harder to keep stable than a larger one — the opposite of what beginners expect. Choose the largest nano you have room for, cycle it fully (see cycling), and avoid the tiny sub-20-litre “betta cubes” that are too small to stay stable.
Our top picks
Best all-rounder — Fluval Flex 57. The Fluval Flex 57L hides its filtration neatly, includes good LED lighting, and at 57 litres is stable enough for a small community.
Best for aquascaping — Aqua One / clear-glass rimless. A rimless 30L nano gives the clean, modern look for a planted scape or shrimp tank.
Best shrimp/betta tank — Fluval Spec. The Fluval Spec is a smart, well-filtered small tank ideal for a single betta or a cherry shrimp colony.
What to stock
Great nano stock includes ember tetras, cherry shrimp, a single betta, nerite snails and small rasboras. See how many fish fit before stocking.
Frequently asked questions
What is a nano aquarium?
A nano aquarium is a small tank, roughly 20–60 litres, designed for shrimp, bettas and small shoaling fish. All-in-one models include built-in filtration and lighting.
Are nano tanks good for beginners?
They can be, but smaller water volumes swing faster in temperature and chemistry, so they are less forgiving than larger tanks. Choose the largest nano you can fit and cycle it fully before adding livestock.
What fish can live in a nano tank?
Small species such as ember tetras, chili rasboras, a single betta, cherry shrimp and nerite snails. Always check stocking limits before adding fish to a small volume.
— Jaqline Smalling, FishForever
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