Pseudomugil cyanodorsalis, the Neon Blueeye or Blueback Blueeye Rainbowfish, is one of those rare, arcane Rainbowfishes that I think most of us only dream about, so when the opportunity came around to make them more available to the hobby and trade, I absolutely jumped at it. This is a schooling fish, I would not recommend purchasing only one or two as you’ll not get to see the males fired up and showing off; most sources recommend 8-10 or more. This species is on the small side for the Blue Eyes, but beyond its obvious overtly good looks, its predilection for being a brackish-water fish is the one thing probably preventing it from being a ubiquitous worldwide hit like the related Furcata Rainbowfish.
In the short time I’ve kept this fish, I’ve placed it in everything from nearly pure freshwater (with just one tablespoon marine aquarium salt per 5 gallons of water) to full strength saltwater right alongside young clownfishes and Peppermint shrimp. Experienced keepers suggest aiming for the middle, somewhere in the 1.010 to 1.015 specific gravity range, as being ideal for breeding and maximizing production. Indeed, by default I keep these at roughly 1.012 here (because I simply mix my saltwater supply with tap water in a 1:1 ratio). Keeping them brackish might at first cause you to feel very limited in tankmate choices, but the one fish that jumps out at me as perfectly suited is the often overlooked Bumblee Bee Goby.
While I’ll normally ship out at 1.012, know that I’ve moved from from that salinity to either extreme without any acclimation had have had no losses. With advanced notice, I’m more than happy to move the fish over prior to shipment so they can arrive at your preferred salinity. I mentioned they’re tiny; expect them to ship to you at roughly 0.5 to 0.75 inches. Nano fish in every sense.
These Rainbowfish are locally produced and raised here in Minnesota; I view it as a special treat to be able to support a local breeder and I hope to see this become a staple offering. If that’s not possible, this is one of those rare fishes I may just have to breed myself!