Blue Back Blue Eye
Pseudomugil cyanodorsalis
A tiny, highly active euryhaline species native to the mangrove swamps and tidal estuaries of Northern Australia. While biologically capable of surviving in pure freshwater or full marine conditions, they require a brackish aquarium (SG 1.005-1.015) to thrive, breed, and resist disease long-term. They are peaceful shoaling fish but spectacular jumpers, so a tight-fitting lid is absolutely mandatory.
Blue Back Blue Eye At a Glance
Blue Back Blue Eye Tank Requirements
Will Blue Back Blue Eye fit in your tank?
Care guides tell you what Blue Back Blue Eye needs, the next question is whether your tank can safely provide it. Test Blue Back Blue Eye against your tank size, maintenance needs, and the fish you already keep before you buy.
Blue Back Blue Eye Water Parameters
Blue Back Blue Eye Temperament & Compatibility
Blue Back Blue Eye Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Males boast a striking metallic neon-blue stripe running along their upper back, with distinctive yellow and black edges on their extended dorsal and anal fins. They frequently flare their fins to spar with rival males for hierarchy, though no actual damage is done.
Differs in 2 traits from base species
Also known as: Male Neon Blue Eye
Female
Females are plainer, lacking the vivid blue back and having shorter, clear or faintly yellowish fins. They possess a slightly fuller belly. Keeping more females than males helps disperse male courting attention.
Differs in 1 trait from base species
Also known as: Female Blueback
Blue Back Blue Eye Care Guide Summary
The Blue Back Blue Eye, scientifically known as Pseudomugil cyanodorsalis, belongs to the Rainbowfish family group. Adults reach a maximum size of approximately 3.5 cm and have a fusiform body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a low level of biological waste.
To thrive, the Blue Back Blue Eye requires a brackish required aquarium with a minimum volume of 38 litres and a tank length of at least 45 cm. Water temperature should be maintained between 22°C and 30°C, with a pH range of 7–8.5 and a general hardness of 10–30 dGH. A moderate water flow is preferred.
The Blue Back Blue Eye is a rewarding species to keep, provided its core environmental needs are met. This species is available in 2 varieties: Male and Female. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Blue Back Blue Eye Habitat Setup
When setting up an aquarium for the Blue Back Blue Eye, a moderate water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include a sand substrate to accommodate their sifting behaviour and driftwood, which can serve as both a hiding place and a dietary supplement. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Blue Back Blue Eye Compatibility Notes
Classified as peaceful, the Blue Back Blue Eye is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.
Who Blue Back Blue Eye Is Actually For
Blue Back Blue Eye is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 6. It makes the most sense for a hobbyist who will actually build around its needs, especially driftwood.
The most common mistake is treating Blue Back Blue Eye like any other community fish and skipping the soft sand it needs to forage safely. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.
Blue Back Blue Eye Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Blue Back Blue Eye.
10 Gallon Standard
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
Show 22 more tank sizes
Frequently Asked Questions About Blue Back Blue Eye
How big does Blue Back Blue Eye get?
Blue Back Blue Eye (Pseudomugil cyanodorsalis) typically reaches a maximum adult size of approximately 3.5 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does Blue Back Blue Eye need?
A minimum aquarium volume of 38 litres and a tank length of at least 45 cm are recommended for Blue Back Blue Eye. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Blue Back Blue Eye need?
Blue Back Blue Eye thrives in brackish required conditions with a temperature range of 22–30°C, a pH between 7 and 8.5, and a general hardness of 10–30 dGH. A moderate water flow is preferred.
Is Blue Back Blue Eye peaceful or aggressive?
Blue Back Blue Eye is classified as peaceful with an aggression score of 2 out of 10. They are generally well-suited to peaceful community tanks.
How many Blue Back Blue Eye should be kept together?
Blue Back Blue Eye is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Blue Back Blue Eye have any special tank requirements?
Yes. Blue Back Blue Eye benefits from driftwood (digestion/hiding) and sand (sifters) in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Blue Back Blue Eye need a lid on the tank?
Yes. Blue Back Blue Eye is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
Useful setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 2, 2026
- Last updated
- May 2, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for Blue Back Blue Eye
These fish are strong compatibility matches for Blue Back Blue Eye based on water preferences, temperament, adult size, and tank behavior.
Fiddler Crab (Brackish)
Uca sp.
Ideal Tank MatesOrange Chromide
Etroplus maculatus
Ideal Tank MatesX-Ray Tetra (Pristella)
Pristella maxillaris
Ideal Tank MatesWrestling Halfbeak
Dermogenys pusilla
Ideal Tank MatesScat (Brackish)
Scatophagus argus
Ideal Tank MatesJapanese Ricefish (Medaka)
Oryzias latipes
Ideal Tank MatesPlants That Suit Blue Back Blue Eye
These plants pair well with Blue Back Blue Eye based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Dwarf Hairgrass
Eleocharis parvula
Dwarf Sagittaria
Sagittaria subulata
Italian Val
Vallisneria spiralis
Java Fern
Leptochilus pteropus
Java Moss
Taxiphyllum barbieri
Jungle Val
Vallisneria americana
Fish Similar to Blue Back Blue Eye
Delicate Blue-Eye
Pseudomugil tenellus
The Delicate Blue-Eye is a small, highly active shoaling fish native to the swamps and coastal floodplains of Northern Australia and New Guinea. They are euryhaline (tolerating both fresh and brackish water) and thrive in warm, densely planted aquariums. They are peaceful but require a group to feel secure and display their best behaviors.
Kiunga Blue Eye
Kiunga ballochi
A tiny, critically rare micro-predator native to a very restricted area in the Upper Fly River system of Papua New Guinea. Characterized by a transparent 'glass' body with striking yellow and black fin margins. They are peaceful shoaling fish that require highly stable water conditions and a planted aquarium. Listed as Endangered on the IUCN Red List, they are a true rarity in the aquarium trade.
Honey Blue Eye
Pseudomugil mellis
A rare, stunning nano shoaling fish endemic to the acidic, tannin-stained 'wallum' heathlands of Queensland, Australia. Known for their honey-golden bodies and striking blue eyes, they are highly active but peaceful. They require mature, slightly acidic, soft water aquariums with dense planting. Listed as Endangered in the wild.
Popondetta Blue-eye
Pseudomugil connieae
The Popondetta Blue-eye is a stunning, active nano fish native to the clear, fast-flowing streams of Papua New Guinea. Recognized by their bright blue eyes and striking finnage, they are an excellent choice for peaceful community aquariums. As a schooling species, they establish a pecking order, with males frequently flaring their fins in beautiful displays to attract females or establish dominance. They require well-oxygenated, moderately hard, alkaline water to thrive.
Pacific Blue Eye
Pseudomugil signifer
An energetic and highly adaptable blue-eye species native to Eastern Australia. They inhabit a massive range of environments from rainforest streams to full-marine mangrove estuaries. Known for their striking blue eyes and the male's butterfly-like fin displays. They must be kept in schools, where males will constantly spar and flash their colors.
Gertrude's Spotted Blue-eye
Pseudomugil gertrudae
A stunning, highly active nano fish native to Australia and New Guinea. Known for their striking blue eyes and the males' spectacular, heavily spotted fins which they flare during dominance displays. They are peaceful but require being kept in shoals to thrive and exhibit natural behaviors.