Can flowerhorns live with harlequin rasboras?

Verdict

No. Flowerhorns and harlequin rasboras should not share a tank. An adult flowerhorn eats fish that fit in its mouth, and at 2 inches harlequin rasboras do.

Flowerhorn80–89°F · pH 7–8

Harlequin rasbora72–80°F · pH 6–7.5

What to watch

Deal breakerAn adult flowerhorn eats fish that fit in its mouth, and at 2 inches harlequin rasboras do.
Deal breakerFlowerhorns are aggressive and will bully peaceful harlequin rasboras.
Watch outThey only share 80°F. Keep the heater set there and steady.
Watch outFlowerhorns grow to 12 inches and need 75 gallons, far more than a tank set up for harlequin rasboras.

What works

pH 7–7.5 suits both.

Water side by side

The green band is the temperature range both can live in.

The green band is the pH both tolerate.

Size to scale

Adult length in an aquarium. A fish can swallow anything that fits in its mouth, roughly a third to half its own length for predators.

Care at a glance

	Flowerhorn	Harlequin rasbora
Temperature	80–89 °F	72–80 °F
pH	7–8	6–7.5
Adult size	12.0 in	2.0 in
Minimum tank	75 gal	10 gal
Temperament	Aggressive	Peaceful
Swims at	Middle	Middle
Group	One per tank	Groups of 6+
Diet	Carnivore	Omnivore

Better tank mates for harlequin rasboras

All harlequin rasbora tank mates

Questions

Can flowerhorns live with harlequin rasboras?

No. Flowerhorns and harlequin rasboras should not share a tank. An adult flowerhorn eats fish that fit in its mouth, and at 2 inches harlequin rasboras do.

What temperature suits both flowerhorns and harlequin rasboras?

80–80 °F. Flowerhorns need 80–89 °F, harlequin rasboras need 72–80 °F.

What size tank do flowerhorns and harlequin rasboras need together?

At least 75 gal, set by the flowerhorn. Add space for each extra fish.