Tetras

Tetras are the backbone of the community tank: small, colorful and happiest in a proper school. Most want soft, slightly acidic water and a group of six or more. Each profile lists the tank size and conditions a species does best in.

Tank size: 5–264 gal; 5 gal (20 L) to 264 gal (1,000 L); half the list needs 18 gal (70 L) or more
Temperature: 72–81°F; 22–27°C, most of the list
pH: 5.5–7.2; Most of the list
Difficulty: 45 easy; 97 medium · 6 difficult
Temperament: 126 peaceful; 21 mostly peaceful · 1 aggressive

148 species and 3 varieties

Tetras for a community tank

The community tetras are the fish the hobby is built on, and the profiles separate them on tank size and temperature. The neon tetra stays at 1.5 inches (3.75 cm), lists 10 gallons (40 liters) and wants cooler water than most people give it, 70–77°F (21–25°C). The cardinal tetra is a little larger at 1.8 inches (4.5 cm), lists 15 gallons (60 liters) and runs warm, 73–84°F (23–29°C). The ember tetra is the nano fish of the group at under an inch (2 cm). The rummy-nose tetra is the tightest schooler, 2 inches (5 cm) in 20 gallons (75 liters). The glowlight, black neon, lemon and X-ray tetras are the forgiving middle: 1.4 to 2 inches (3.5 to 5 cm), 15 to 20 gallons (60 to 75 liters), and forgiving about water; the lemon and X-ray tetras list pH up to 8.

Six is the minimum, ten is better

Nearly every tetra here is a schooling fish. In a group of three they hide, lose colour and pick at each other; in a group of ten they swim in the open and behave. One species in numbers beats three species in threes, both for the fish and for the look. The rummy-nose is the useful one: its nose fades when the water is off, before anything else in the tank shows a problem.

Match the water

Most tetras list soft to neutral water and 72–82°F (22–28°C), and the common species adapt to a wide range. The blackwater specialists do not: the tucano tetra, the hummingbird tetra, the adonis tetra and Axelrod's glass tetra list pH no higher than 6.5 and are marked difficult, and they belong in a peat-stained tank, not a community. At the other end, the X-ray, lemon, bloodfin, silvertip, Buenos Aires and blind cave tetras list pH up to 8 and are the tetras for hard tap water. Temperature is the quiet killer: the neon tetra tops out at 77°F (25°C), so a neon in an 82°F (28°C) discus tank is living short.

The nippers and the plant eaters

A few tetras earn their reputation. The serpae tetra and the black widow tetra are marked peaceful and mostly peaceful in the catalog, and they earn it only in a school: in threes and fours they nip fins and each other, in a school of eight or more they keep it among themselves, and neither belongs with a betta or a long-finned guppy. The Buenos Aires tetra is hardy, grows to 3 inches (7.5 cm) and eats soft plants down to the stem. The bucktooth tetra is the outlier: a scale eater marked aggressive, kept in a species tank in a group of twelve or more so no single fish takes the damage.

Not every tetra is small

The Congo tetra reaches 3 inches (8 cm), lists 25 gallons (90 liters) and is the best known of the African tetras, which have longer fins and want more room than their South American cousins. The diamond, bleeding heart, emperor and penguin tetras sit between 2 and 2.5 inches (5 and 6.5 cm). The silver dollars are filed here too, at 6 inches (15 cm) in 70 gallons (265 liters), and they eat plants. The blind cave tetra reaches 5 inches (12 cm), the nurse tetra 10 inches (25 cm), and the red-tail brycinus, an African relative at 21 inches (53 cm) on 264 gallons (1000 liters), is the largest fish on this page. The family's two giants, the African tigerfish and the goliath tigerfish, are kept off this list on purpose: at 30 inches (75 cm) and 52 inches (133 cm) they are predators, not tetras, and they have their own profiles under monster fish.

By the numbers

Smallest

Largest

Easiest to keep

Fits a 20 gallon tank

Fits a 30 gallon tank

FAQ

Common questions

How many tetras should be kept together?

Six at least, ten or more if the tank allows, of one species. They are schooling fish and behave badly in small groups.

What size tank do neon tetras need?

10 gallons (40 liters) for a school of six to eight. They stay at 1.5 inches (3.75 cm).

What temperature do tetras need?

Most list 72–82°F (22–28°C). Neons run cooler at 70–77°F (21–25°C); cardinals run warmer, up to 84°F (29°C); green neons list 72–86°F (22–30°C). The range is on each profile.

Can neon tetras live with cardinal tetras?

Yes, but their ranges only overlap at 73–77°F (23–25°C). Set the heater there and pick one of the two as the school you build up.

How big do tetras get?

Most stay between 1 and 2.5 inches (2.5 and 6 cm). The Congo tetra reaches 3 inches (8 cm) and the silver dollars 6 inches (15 cm). The red-tail brycinus, at 21 inches (53 cm), is the largest fish on the page; the two tigerfish are relatives kept off this list.