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: 6.0–7.2; Most of the list
Difficulty: 26 easy; 115 medium · 44 difficult
Temperament: 120 peaceful; 60 mostly peaceful · 5 aggressive

185 species and 7 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 smallest of the three and lists 7 gallons (25 liters), marked medium because it wants soft water and small food. The neon tetra is the classic at 1.5 inches (3.75 cm) for 11 gallons (40 liters), marked beginner. Endler's livebearer is 1.6 inches (4 cm) for a 5 gallon (20 liter) tank and breeds without help, and the least killifish is a 1.4 inch (3.5 cm) livebearer marked easy for the same tank.

The rule

What makes a freshwater fish nano

Every fish on this page stays under 2.4 inches (6 cm) and lists 11 gallons (40 liters) or less. Small does not mean solitary: most of them are schooling fish, and a group of eight to ten of one species in a 10 gallon tank is the right way to keep them, not one of each. They eat small food, crushed flake, micro pellets and baby brine shrimp, and they eat often. And a small tank has no buffer, so the water changes are weekly and the stocking stays light.

01
Under 2.4 inches
Every fish here stays under 6 cm full grown
02
11 gallons or less
Every profile lists 40 liters or under
03
Still a school
Eight to ten of one species, not one of each
04
Small food, often
Crushed flake, micro pellets, baby brine shrimp

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 easy, which makes it the smallest easy fish in the catalog. 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, and the most forgiving school on this page.

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, and 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 the hardest fish on this page: 1.1 to 1.5 inches (2.7 to 3.8 cm), a 5 to 11 gallon (20 to 40 liter) tank, a pH from 3.5 to 6 and water so soft it comes from a reverse osmosis unit. The wine-red betta and the other small wild bettas want the same water at 1.4 inches (3.5 cm) for 11 gallons (40 liters). 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?

Endler's livebearer, the least killifish and the dwarf livebearer all list 5 gallons (20 liters) and are marked beginner or easy. The chili rasbora lists 7 gallons (25 liters) and 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, plus one centerpiece such as a scarlet badis. Check the mix in the stocking calculator before adding a second school.

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?

Bettas are not on this list because they list a larger tank, but a betta shares a 10 gallon tank with a school of ember tetras or chili rasboras in many tanks. Check the pair in the stocking calculator, and 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.

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.

Index