Galaxy Rasbora

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Scientific name: Danio margaritatus

Common name: Galaxy Rasbora

Family: Cyprinidae

Recommended pH range for the species: 6.5-7.5

Recommended water hardness (dGH): 1-5

Recommended temperature: 22 - 26 °C (71.6 - 78.8°F)

New species of fish are being discovered all of the time but most are just merged into the aquarium trade without a great impact, one species that has proven to be a massive hit with fish keepers has to be the Galaxy Rasbora. This fish with its amazing colouration has taken the market by storm even though it has only been available in the last 5 years. This beautiful but undemanding fish is so striking that when pictures first appeared of it, many people were sceptical and believed that all of the pictures had been doctored somehow to enhance the true colours of the fish as some form of marketing ploy.

The Galaxy Rasbora has proven them wrong and is even more stunning when seen in its aquarium than any picture could hope to replicate. They were first discovered in 2006 in Myanmar in a small area near the Salween basin and they are already proving to be difficult to catch for sale due to their small numbers.

Recently their name has changed from the Galaxy Rasbora to Celestial Pearl Danio as it was found to be more closely related to the Danios and further studies have backed this up. The official name for this fish when first discovered was Microrasbora sp.”Galaxy”, it has now adopted the official name of Danio margaritatus. The fish has a somewhat strange body shape compared to its close relatives, it has a somewhat stumpy nose and its body length is about 3 times its height, its for this reason that it was first classed with the Microrasboras. The males and females display a large difference in their colouration, the males have a bright blue body colouration and more colour in their finnage , the females display a duller bluish green background and they will also have a yellowish tint to their bellies. Both sexes have a patterning of small dots and their gill plates are transparent so that the blood vessels are clearly visible.

Caring for the Galaxy Rasbora

Their natural habitat is small ponds that are slightly alkaline and the temperatures rarely reach above 24°C (75.20°F) but as the water is always very shallow, temperature changes through the day are inevitable but these fish have adapted to this. In the aquarium they do not need a lot of space, they spend long periods of time motionless and even though they should be kept in groups of at least 6 specimens, they do not stay close together and can often be seen separated in their own small spots. They do not like high temperatures and even though they do like soft water, it should not be acidic. Add plenty of plants to the aquarium and they will require some hiding places if they feel threatened so add either wood or rocks to provide these. The lighting should not be too strong but as they hail from shallow water, the lighting should reach the bottom of the tank, using a shallower tank than normal will help with this. If you are keeping these with a view to breeding them, add clumps of Java Moss or a spawning mop that will blend in with the other décor as this will give the fry a chance to escape from their parents.

Although these fish are regarded as being quite hardy it is not advised to add these to an aquarium that has recently been set up due to the unstable water parameters, they will fair much better in an established tank. Keep these fish with similar species that prefer the alkaline conditions, they may have small bouts of fin-nipping with their tank mates but this should not be too serious.

The Galaxy Rasbora has a very small mouth so the size of the food should take this into account. They are not fussy eaters and should accept high quality commercial flakes but they do seem to prefer small live or frozen foods. Cyclopeeze and Mysis are readily accepted but you can also feed them with brine shrimp, chopped blood worms and cultured white worms.

Breeding the Galaxy Rasbora

Spawning with these fish in their natural habitat is very sporadic and unlike most fish species they do not seem to have spawning seasons when the food is plentiful or the water conditions are right. This proves to be beneficial to any potential breeder as supplying the fish with their needs for spawning is made a lot simpler.

Use a shallow tank fitted with an air driven sponge filter and add Java Moss or a spawning mop, substrate is optional and for tank hygiene it is easier with a bare bottomed tank. Set the temperature to approx 24°C (75.20°F) and introduce the parent fish. The parents do not need a lot of conditioning to get them prepared for spawning but a few extra meals of live or frozen foods certainly helps. The males will start to dance around the females and display to her, the males colouration may darken slightly but not in all cases. Eventually the male will start to drive the female into the spawning mop or moss trying to persuade her to lay her eggs. Once she starts to deposit the eggs, the male will dart into the spawning site to fertilise them. Only a few eggs are laid each time and this process is repeated over a number of hours.

The eggs will be very tiny and should hatch after 24 hours. It is often the case that the breeder does not realise eggs have actually been laid until the fry can be seen attached to the tank glass or in the moss, they have the appearance of slivers of glass themselves. It is best to syphon out the fry into a separate tank as the parents will try to eat them, keep checking the tank until you are sure that there are no more fry to be found.

Initial growth of the fry is very slow but this should speed up after a few weeks. It is best to feed them Infusoria initially due to their small size, as they grow the diet can be changed to newly hatched brine shrimp. They will need feeding 3-4 times per day but only add small amounts of food so that the water does not get polluted.