Harlequin Rasbora: Tank Size, Tank Mates & How Many to Keep

What size tank do harlequin rasboras 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: Trigonostigma heteromorpha.

How many harlequin rasboras in each tank size?

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

Tank	How many harlequin rasboras
5 gallon	Too small
10 gallon	Too small
20 gallon long	up to 12
29 gallon	up to 18
40 gallon breeder	up to 25
55 gallon	up to 35
75 gallon	up to 47
125 gallon	60 or more

Check harlequin rasboras against your own tank and other fish

Good to know

Keep at least 6. Alone or in twos and threes, harlequin rasboras hide, stop eating well, or pick on each other.

Tank mates for harlequin rasboras

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 harlequin rasbora.
Molly: They need different water: Harlequin rasbora likes a pH of 5.5–7.5, molly likes 7.5–8.5.

Questions and answers

What size tank do harlequin rasboras 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 harlequin rasboras should be kept together?

At least 6. Harlequin rasboras are social animals and only behave naturally in a group. More is better if the tank has room.

Can harlequin rasboras live in a 10 gallon tank?

No. Harlequin rasbora needs at least 15 gallons (57 liters).

What temperature do harlequin rasboras need?

72–81 °F (22–27 °C), with a pH of 5.5–7.5. In most homes that means a heater.

Can harlequin rasboras live with a betta?

Usually, yes, in a tank of 15 gallons (57 liters) or more. They like the same water: 75–81 °F (24–27 °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.