Celestial Pearl Danio

Scientific name: Celestichthys margaritatus, also listed as Danio margaritatus

Adult size: about 2–2.5 cm

Origin: Shan State, Myanmar

Water: 20–26 °C, pH 6.5–7.5, 5–15 dGH

Group: 10 or more, the more the better

Diet: tiny live, frozen and dried foods

Temperament: peaceful but timid; will hunt shrimp fry

The celestial pearl danio, still widely sold as the galaxy rasbora, is a tiny fish of about 2–2.5 cm patterned with pearl-white spots over a deep blue body and red-and-black barred fins. It was discovered in 2006 in shallow, plant-filled ponds near Hopong in Shan State, Myanmar. It is shy on arrival and easily out-competed at feeding time, so it shows best in a quiet, densely planted tank with other small, calm fish rather than a busy community. It is a shoaling fish and behaves most naturally in numbers; Seriously Fish suggests buying as many as possible, ideally 20 or more, and Aquarium Co-op recommends at least six with 10–15 strongly preferred. Males spar with each other during the day and occasionally nip fins within the group, but rarely bother other species. Aquarium Co-op notes results with cherry shrimp are mixed and that celestial pearl danios will hunt baby shrimp if given the chance.

Water: 20–26 °C and pH 6.5–7.5, hardness 5–15 dGH, so neutral to slightly alkaline and moderately hard. It tolerates cooler rooms than many tropicals, and Aquarium Co-op suggests 22–24 °C as a comfortable band.

Tank and planting: dense planting with mosses and fine-leaved plants, plus plenty of hiding spots. Keep flow gentle and lighting moderate; floating plants help the fish settle.

Feeding: tiny slow-sinking foods: baby brine shrimp, frozen cyclops and daphnia, microworms and crushed flake. Small live foods bring out the strongest colour.