Nano freshwater fish

Nano fish stay small enough for a desktop tank without feeling cramped. Every species here suits roughly a 10 gallon or smaller and stays under a few inches full grown. Profiles list adult size, minimum tank and how each fish behaves in a group. The marine equivalents, mostly tiny gobies, have a list of their own.

Tank size: 5–11 gal; 5 gal (20 L) to 11 gal (40 L); half the list needs 11 gal (40 L) or more
Temperature: 72–81°F; 22–27°C, most of the list
pH: 6.0–7.5; Most of the list
Difficulty: 31 easy; 121 medium · 45 difficult
Temperament: 130 peaceful; 62 mostly peaceful · 5 aggressive

197 species and 18 varieties

Start here

Six fish for a 10 gallon tank

The ember tetra is the nano fish to start with: 0.8 inches (2 cm), a 9 gallon (35 liter) minimum, marked easy and peaceful, and orange enough to see from across the room. The celestial pearl danio is the same size and rating with a spotted body and red fins. The chili rasbora is the same size and lists 10 gallons (38 liters), marked medium because it wants soft water and small food. The pygmy cory schools in mid-water at 1.3 inches (3.3 cm) and lists 10 gallons (38 liters) too. Endler's livebearer is 1.6 inches (4 cm) for a 10 gallon (38 liter) tank and breeds without help. The least killifish is a 1.4 inch (3.5 cm) livebearer marked easy for a 5 gallon (20 liter) tank.

The rule

What makes a freshwater fish nano

Every fish on this page stays at 2.4 inches (6 cm) or under and lists 11 gallons (40 liters) or less. The schooling fish here want a group of eight to ten of one species in a 10 gallon tank, not one of each. Wild bettas, badis, darios, licorice gouramis and many killifish are kept singly, in pairs or as one male with a few females. All of them eat small food, and they eat often. The darios, badis, licorice gouramis, glassfish and bumblebee gobies often refuse flake and need live or frozen food. And a small tank has no buffer, so the water changes are weekly and the stocking stays light.

01
2.4 inches or less
Every fish here is 6 cm or smaller full grown
02
11 gallons or less
Every profile lists 40 liters or under
03
Schools and pairs
Eight to ten of a schooling species, or a pair of wild bettas or badis
04
Small food, often
Live or frozen baby brine shrimp, and crushed flake for fish that take it

Micro schools

Micro rasboras and the smallest tetras

The exclamation-point rasbora stays at 0.6 inches (1.6 cm), lists 11 gallons (40 liters) and is marked medium, because it needs a mature, stable tank. The phoenix rasbora and the dwarf rasbora are its Boraras cousins at 0.8 to 1 inch (2 to 2.5 cm), marked medium for their soft water and their shyness in small numbers. The flame tetra is a 1 inch (2.5 cm) fish for 10 gallons (38 liters), marked easy, and the jellybean tetra is its African counterpart at 1.2 inches (3 cm). The espei rasbora is the harlequin's smaller relative at 1.5 inches (3.8 cm) for 11 gallons (40 liters), marked easy. The neon tetra, gold ring danio and medaka are the only schooling fish here marked beginner.

Centerpieces

One fish to build a nano tank around

The scarlet badis is a 0.8 inch (2 cm) fish that hunts live and frozen food and ignores flake, marked medium and mostly peaceful, and one male with a few females owns a 10 gallon tank. The gold ocellatus is a Tanganyikan shell dweller at 2.4 inches (6 cm) for 11 gallons (40 liters), marked easy, and it wants hard water at a pH from 7.5 to 9 and a pile of snail shells. The golden lyretail killifish is 2.4 inches (6 cm) for 10 gallons (38 liters) and jumps, so the lid matters. The medaka is the cool one, marked beginner at 61–72°F (16–22°C), a rice fish for an unheated tank. The green panchax is a 2 inch (5 cm) surface fish marked easy. It eats tank mates small enough to swallow, so keep it away from ember tetras and other 0.8 inch (2 cm) fish. The red melon dario is the scarlet badis's larger cousin at 1.2 inches (3 cm).

Specialists

The blackwater specialists

The licorice gouramis are among the fish marked difficult on this page. They are 0.9 to 1.6 inches (2.4 to 4 cm) for 5 to 11 gallons (20 to 40 liters). Most list a pH from 4.5 to 6, and the whole group runs from 3.5 to 6.8. Their water is so soft it comes from a reverse osmosis unit. The wine-red betta is 1.4 inches (3.5 cm) for 11 gallons (40 liters) and wants the same water. Most of the small wild bettas here do too. The Mahachai betta wants hard, alkaline water with a pH from 7 to 8.5 instead. The sundadanios are 0.9 inch (2.3 cm) schooling fish for a pH from 4.5 to 6.5, marked difficult. The pygmy carplet is 0.5 inches (1.2 cm), one of the smallest fish anyone keeps, and the Tambopata glass tetra is 0.7 inches (1.9 cm) for a 5 gallon (20 liter) tank. None of them belongs in a first tank.

By the numbers

Smallest

Largest

Easiest to keep

Most peaceful

FAQ

Common questions

What fish can live in a 5 gallon tank?

The least killifish and the dwarf livebearer list 5 gallons (20 liters) and are marked easy. Most licorice gouramis, the pygmy carplet and several other nano fish also list 5 gallons (20 liters) but are marked medium or difficult. Endler's livebearer and the chili rasbora list 10 gallons (38 liters). Most of the other nano fish list 9 to 11 gallons (35 to 40 liters).

How many nano fish fit in a 10 gallon tank?

A school of eight to ten of one species, such as ember tetras or chili rasboras, fills it. A scarlet badis beside that school wants a 15 gallon tank. Check the mix in the stocking calculator before adding a second species.

Are nano fish harder to keep than bigger fish?

The fish are not; the ember tetra, celestial pearl danio and Endler's livebearer are marked easy or beginner. The tank is: 10 gallons of water swings faster than 40, so the water changes have to happen on time.

Can a betta live with nano fish?

The betta is not on this list because it grows to 3 inches (7.5 cm), past the 2.4 inch (6 cm) limit. The small wild bettas, such as the wine-red betta, are on it. Many keepers put a betta with six ember tetras or chili rasboras, but the stocking calculator reads that as too full for a 10 gallon tank. The same fish fit a 15 gallon. Read the betta hub before you try it.

Do nano fish need a heater?

Most list 72–82°F (22–28°C) and need one. The medaka lists 61–72°F (16–22°C) and does better without. The Everglades pygmy sunfish lists 54–82°F (12–28°C) and needs no heater in a normal room. Cool-range fish such as the torpedo badis, Asian stone catfish, fighting gaucho and Ogowe killifish top out at 73–77°F (23–25°C).

What do nano fish eat?

Crushed flake, micro pellets, baby brine shrimp and daphnia, fed in small amounts twice a day. The scarlet badis and the darios refuse dry food and need frozen or live food from the start. Other badis, the licorice gouramis, glassfish, bumblebee gobies, Everglades pygmy sunfish, blackstripe dwarf cichlid and Asian stone catfish often refuse it too.

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