Tank setup
The Complete Nano Aquarium Guide
How to set up and stock a nano aquarium under 40 litres, the best nano fish, shrimp and plants, why small tanks are less forgiving, and how to keep one stable.
Updated 3 min read
Part of our complete planted-aquarium guide.
The short answer
A nano aquarium, anything under about 40 litres, lets you build a complete planted scape on a desk or shelf. The catch is that a small water volume is less forgiving: temperature, pH and pollutants swing faster than in a big tank, so nano tanks reward stability and punish overstocking. Keep the stocking tiny and peaceful (a single small school of nano fish, or a shrimp colony), use a gentle filter and a small heater, plant heavily, and be disciplined about light feeding and small regular water changes. Do that and a nano tank is one of the most rewarding formats in the hobby.
Small tank, big rules
The whole art of a nano tank is understanding that less water means less buffer. A heater failure, a missed water change, or a handful too much food hits a 20 litre tank far harder than a 200 litre one, because there is less water to dilute the problem. So the guiding principle is stability over ambition: understock, feed lightly, and keep a steady maintenance routine. Heavy planting helps a lot, because plants soak up waste and steady the tank.
Equipment for a nano
- Filter: a small sponge filter or a nano internal, run gently so it does not blast tiny fish and shrimp around. See filtration.
- Heater: a small heater keeps temperature steady, which matters most in low volume. See heaters.
- Light: a nano LED is plenty. Keep the photoperiod to six to eight hours to hold algae off in the small volume.
- Flow: gentle and even. Read circulation and flow.
The best nano fish
Nano tanks demand genuinely small, peaceful fish. Stick to micro species and keep one small school, not a mix.
Chili Rasbora
Boraras brigittae
Southwestern Borneo blackwater swamps
Ember Tetra
Hyphessobrycon amandae
Rio das Mortes basin, Brazil
Celestial Pearl Danio
Danio margaritatus
Hopong area, Myanmar
These stay tiny, school beautifully, and suit a nano's scale. Avoid anything that outgrows a few centimetres, and skip boisterous or nippy fish, which have nowhere to escape each other in a small tank. Use the compatibility tool and tank planner to keep it sensible.
Or go shrimp-only
A shrimp-only nano is arguably the best use of a small tank. A colony of cherry shrimp turns a nano into a living, breeding, foraging little world, and needs no heater-hungry tropical fish.
Red Cherry Shrimp
Neocaridina davidi
Taiwan (selectively bred)
Shrimp are sensitive to swings, so a stable nano suits them, and a heavily planted tank gives them the biofilm and cover they love.
Plants for a nano
Scale matters. Small-leaved, slow plants keep a nano looking in proportion.
Bucephalandra (mixed)
Bucephalandra sp.
Borneo (rheophytic)
Monte Carlo
Micranthemum tweediei
Argentina
Bucephalandra and anubias on small pieces of hardscape, a fine carpet like Monte Carlo, and a little moss suit the scale. Big fast stems overwhelm a nano and need constant trimming. See aquascaping design for composing a small scape, where restraint and open space matter even more.
Keeping it stable
The nano keeper's habits: understock, feed a tiny pinch, change a small amount of water often (a fifth every week is easy at this size), and never let the heater or filter go unchecked. Cycle it fully before stocking, just like any tank, and watch the numbers closely, because they move fast in low volume.
FAQ
The quick answers are above. Next, read how to set up a planted aquarium for the full setup sequence and cherry shrimp care if you go the shrimp route.
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
What is a nano aquarium?
A nano aquarium is a small tank, usually under about 40 litres (10 gallons). It packs a full planted scape and a few tiny fish or a shrimp colony into a compact footprint, but the small water volume makes it less forgiving of mistakes than a larger tank.
What fish can live in a nano tank?
Only genuinely small, peaceful nano fish: chili rasbora, ember tetra, celestial pearl danio, and similar micro species, kept in a small school. Shrimp-only tanks are also excellent. Avoid anything that grows past a few centimetres or is boisterous.
How many fish can go in a nano tank?
Far fewer than people expect. A 20 to 30 litre tank might hold a single small school of one nano species (roughly 6 to 10 fish), or a shrimp colony, not both crammed together. Use the tank planner for your exact volume and understock rather than overstock.
Are nano tanks harder to keep?
Yes. A small water volume swings faster, so temperature, pH and pollutants change quickly and small mistakes hit harder. Nano tanks reward stability: steady stocking, light feeding, and regular small water changes.
Do nano tanks need a filter and heater?
Yes to both. A gentle filter (a small sponge or nano internal) houses the bacteria and moves water, and a small heater keeps the temperature stable, which matters most in a low-volume tank. Keep the flow gentle so tiny fish and shrimp are not blasted around.