Can Harlequin rasbora Live With Neon tetra?

The harlequin is the most accommodating fish in this pairing: exceptionally peaceful, with no special demands on water chemistry, and recommended without reservation to people new to the hobby. It is routinely combined with tetras, and the neon is the tetra most people mean.

Their ranges meet across 21 to 25 °C and pH 5 to 7.5, so a tank at about 24 °C and neutral to slightly acidic water suits both. At 4.5 cm the harlequin is half again the length of a 3 cm neon, which is no threat: it is a micropredator that eats small insects, worms and crustaceans, nothing the size of a tetra.

Both are schooling fish, so buy 8 to 10 of each and give them a base of at least 60 by 30 cm. Both are shown to best effect over a dark substrate with driftwood and patches of shade, with floating plants diffusing the light, which is the layout each is recommended for on its own.