X-Ray Tetra: Tank Size, Tank Mates and How Many to Keep

The X-ray tetra, or pristella, is so clear you can see its backbone. It is among the hardiest tetras and copes with harder water than most.

Adult size
1.8 in4.5 cm
Smallest tank
15 gallons57 liters
How many
6 or more
Temperature
75–82 °F24–28 °C
pH
6–8
Temperament
Peaceful
Swims
In the middle
Heater needed
Yes

What size tank do x-ray tetras need?

At least 15 gallons (57 liters) for a group of 6. The smallest standard tank that works is the 15 gallon. A bigger tank is always easier to keep stable. We give the size for an adult fish in a proper group, because the small fish in the shop will grow. Scientific name: Pristella maxillaris.

How many x-ray tetras in each tank size?

This is how many each standard tank carries comfortably if x-ray tetras are the only fish in it. Share the tank with other species and the number goes down.

TankHow many x-ray tetras
5 gallonToo small
10 gallonToo small
20 gallon longup to 12
29 gallonup to 18
40 gallon breederup to 25
55 gallonup to 35
75 gallonup to 47
125 gallon60 or more

Check x-ray tetras against your own tank and other fish

Good to know

  • Keep at least 6. Alone or in twos and threes, x-ray tetras hide, stop eating well, or pick on each other.

Tank mates for x-ray tetras

These animals like the same water, are a safe size, and have a temper that fits. It is a match on paper: always watch new tankmates for the first week.

Poor matches

  • Fancy goldfish: Goldfish do best with other fancy goldfish.
  • Oscar: Oscar is aggressive and will bully or kill peaceful fish such as x-ray tetra.

Questions and answers

What size tank do x-ray tetras need?

At least 15 gallons (57 liters) for a group of 6. The smallest standard tank that works is the 15 gallon. A bigger tank is always easier to keep stable.

How many x-ray tetras should be kept together?

At least 6. X-ray tetras are social animals and only behave naturally in a group. More is better if the tank has room.

Can x-ray tetras live in a 10 gallon tank?

No. X-ray tetra needs at least 15 gallons (57 liters).

What temperature do x-ray tetras need?

75–82 °F (24–28 °C), with a pH of 6–8. In most homes that means a heater.

Can x-ray tetras live with a betta?

Usually, yes, in a tank of 15 gallons (57 liters) or more. They like the same water: 75–82 °F (24–28 °C). Every betta has its own temper, so watch closely for the first week and have a spare tank ready.

More fish

Adult size, tank size and water ranges follow the mainstream care consensus (Seriously Fish species profiles and FishBase maximum lengths). Where sources differ we use the more cautious figure. Stocking numbers come from our stocking calculator.