Danio margaritatus was first “found” for the aquarium trade in August 2006 and was quickly described by Roberts as Celestichthys margaritatus, which is where “celestial pearl” comes from. Apparently there was quite a hurry to get the first paper out as a few groups were trying to describe the species at the same time. It was only a year later that the species was moved to the genus Danio by Conway.
This unusual little fish was originally found near the town of Hopong, in the same area as the similar Danio erythromicron, but unlike D. erythromicron, which comes from Inle Lake, D. margaritatus is found in small, shallow ponds with a high amount of vegetation. Over the next few years, more collection points were discovered, including in more areas around Hopong and as far as Thailand.
The fish became so popular due to its small size that in a matter of months, large parts of the habitat where it was originally found had apparently been destroyed, which triggered a blanket ban on export, but the Danios proved easy to breed, so captive bred specimens were almost immediately available. The fish appears to retain its beautiful colour when bred in captivity, while wild caught specimens are difficult to feed, so one should aim to only buy captive bred fish. It would be irresponsible to continue encouraging the destruction of a habitat through purchasing wild caught specimens. A couple of the more positive side effects of this species becoming so popular was the increased income of the local fishermen, who were paid 20 times more per fish when selling to the aquarium trade than when selling the fish locally for food, and an increase in availability of other dwarf species, such as Boraras, in the aquarium trade.
The recorded SL was 21.2 mm for a holotype male and 20.5 mm for a paratype female. It is quite possible that the species may grow slightly larger, especially since the specimens I bought are already around 20 mm, while the breeder said that they would grow another 30%, so would reach around 28.6 mm. Unfortunately, I was not able to see the parent fish to confirm this.
The temperature, as recorded by the closest weather station, which is approximately 400 metres higher above sea level and 30 km away, ranges from an everage low of 8 °C to an average high of 29 °C. From this, I would assume that the water temperature that the fish are found in would be within 15 to 25 °C, which is in line with what the breeder I bought them from told me: he said that the fish showed best colouration at 20-22 °C, losing most of its brilliant colouration at 25-26 °C. I had already assumed as much, which is why I set the aquarium heater to 20 °C as soon as the cycle was complete. This way, the fish should show best colouration for most of the year, only losing it in the summer, when air temperatures reach 30-35 °C.
Due to its natural habitat, this species is most likely best suited for small, shallow and well planted aquaria with low current. 60 × 30 × 30 cm aquarium seems to be ideal for the species as males may fight in smaller aquaria, but the fish “get lost” in larger aquaria. The majority of the plants found in the area were from the Hydrocharitaceae family, although the fish seem content with anything which provides a thick cover.
This species is compatible with most other small, peaceful aquarium fish which prefer plants and a slow current. Most of the Asian species I list as suitable for 60 litre aquariums should be comptible.
The fish’s diet appears to consist mainly of small invertebrates, although they readily take dry foods. For best colour, it is advised that the fish are fed a varied diet, including a large proportion of tiny live foods such as newly hatched Artemia and small water fleas. Due to the small stomach which is appropriate for the size of the fish, I would recommend that this species is fed small amounts of food often, for example, at least twice per day, although I expect that they would do well without food for a few days when kept in planted aquaria.
 Roberts, Tyson R. (2007), “The “celestial pearl Danio”, a new genus and species of colourful minute cyprinid fish from Myanmar”. Raffles Bulletin of Zoology 55(1): 131-140
 Conway, Kevin W., Chen, W.-J., Mayden, R. L. (2008), “The “Celestial pearl danio” is a miniature Danio (s.s) (Ostariophysi: Cyprinidae): evidence from morphology and molecules”. Zootaxa 1686: 1–28
 I do not have access to this reference: Hary, C. (2007), “Celestichthys margaritatus: Perlhuhnbärblinge gibt es nicht nur in Burma” (“Celestichthys margaritatus: pearl chicken Danioninae are not only in Burma”). Die Aquarien- und Terrarien-zeitschrift, 60: 6–9