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Dwarf Neon Blue Eye Rainbow

Pseudomugil cyanodorsalis

Pair of Dwarf Neon Blue-eyed Rainbow over 5X magnification


The Dwarf Neon Blue-eyed Rainbow, Pseudomugil cyanodorsalis, is also known as the Blueback Blue-eye.  In March of 2015, Gary Lange talked about Rainbowfish at the GVAC meeting, and I purchased 2 pair of these fish from him.  It is a very attractive fish with the male having brown leading edges on the elongated dorsal and anal fins and a reflective neon blue over much of his body.  The female has shorter fins, little color, and a fuller belly.  The fish I purchased were only about ½ inch long, but Gary insisted they were breeding adults.  I had my reservations about such tiny fish, but he was correct and they were laying eggs within 2 weeks!  Their maximum size is slightly over one inch.  This is truly a nano fish, and I bred them in a 1 ½ gallon tank.


The Neon Blue-eye comes from northern Australia and southern New Guinea coastal waters that vary from almost pure fresh to full saltwater.  A comfortable temperature range for them is 72 to 88 degrees.  To breed and keep them healthy, Gary recommends using salt to achieve a salinity of 1.017.  This is equivalent to 2 cups of sea salt to 5 gallons of water.  I used that at first and it works just fine to get them to breed.  Later, I cut the amount of salt in half (to aprox. 3 Tablespoons of salt per gallon) and still got good egg production, hatching, and growth of the fry.  These fish are sensitive to nitrates, waste, and acid conditions, so water changes are important.  They are peaceful surface dwelling fish and good jumpers, so keep them covered.  They were fed live baby brine shrimp and small amounts of finely ground flake food at the surface, but they will not eat off the bottom, so regular siphoning is necessary.


The aquarium setup was simple:  cover, sponge filter, bare tank bottom, and 2 small mops hanging from the side.  At first I found few eggs in the mops, but when I siphoned off the waste on the bottom, I found several eggs.  These are very clear and difficult to see and must be candled to locate.  Later, I found more eggs in the mops along with those on the bottom.  They are hard, quite large, and can be easily picked from a dark mop.  The eggs were put in a pan with 1 drop of methylene blue and a slow bubbler.  They hatch in 2 weeks, can eat newly hatched brine shrimp right away, grow quickly, and are sexually mature in 3 months.  Considering their small size and number of eggs produced, the Dwarf Neon Blue-eye is quite prolific!