The Harlequin Rasbora (Trigonostigma heteromorpha) is a species of rasbora characterized by its red hue, diamond-shaped body, and black triangular marking on the latter half of its body.
This peaceful rasbora species will live 6 years on average, and grow to just under 2 inches from nose to tail. These fish should be kept in shoals of at least 3 members. A small shoal of Harlequin Rasbora can live in a 10-gallon aquarium. These fish do best in water temperatures in the mid-70's to low-80's. Keep these fish at a neutral pH and with a weak current. They are generally extremely hardy.
These fish are exceptionally peaceful and are not known to nip other species. They can be kept with any other peaceful aquatic animal. Examples include guppies, platies, small tetra species, small barb species, dwarf gourami, and corydora catfish. Always research the compatibility of the animals you wish to keep together.
(Image credit "Practical Fishkeeping")