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.
Delicate Blue-Eye At a Glance
Delicate Blue-Eye Tank Requirements
Will Delicate Blue-Eye fit in your tank?
Care guides tell you what Delicate Blue-Eye needs, the next question is whether your tank can safely provide it. Test Delicate Blue-Eye against your tank size, maintenance needs, and the fish you already keep before you buy.
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Delicate Blue-Eye Water Parameters
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Delicate Blue-Eye Temperament & Compatibility
Delicate Blue-Eye Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Males exhibit brighter coloration (often with a golden or iridescent sheen) and have slightly more extended dorsal and anal fins used for sparring and courtship displays. Best kept in a ratio of 1 male to 2 females.
Differs in 2 traits from base species
Also known as: Male Blue-Eye
Female
Females are slightly smaller, have shorter fins, and possess a more subdued, translucent silver coloration. They are peaceful and should make up the majority of the shoal to disperse male harassment.
Differs in 2 traits from base species
Also known as: Female Blue-Eye
Delicate Blue-Eye Care Guide Summary
The Delicate Blue-Eye, scientifically known as Pseudomugil tenellus, belongs to the Rainbowfish family group. Adults reach a maximum size of approximately 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 Delicate Blue-Eye requires a brackish tolerant aquarium with a minimum volume of 60 litres and a tank length of at least 60 cm. Water temperature should be maintained between 25°C and 32°C, with a pH range of 5–7.5 and a general hardness of 5–15 dGH. A moderate water flow is preferred.
The Delicate 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.
Delicate Blue-Eye Habitat Setup
When setting up an aquarium for the Delicate 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 dense planting to provide cover, break sightlines, and reduce stress and floating plants to diffuse overhead light and create shaded areas. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Delicate Blue-Eye Compatibility Notes
Classified as peaceful, the Delicate 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.
Delicate Blue-Eye Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Delicate Blue-Eye.
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
40 Gallon Breeder
Show 19 more tank sizes
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Frequently Asked Questions About Delicate Blue-Eye
How big does Delicate Blue-Eye get?
Delicate Blue-Eye (Pseudomugil tenellus) typically reaches a maximum adult size of approximately 5 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does Delicate Blue-Eye need?
A minimum aquarium volume of 60 litres and a tank length of at least 60 cm are recommended for Delicate Blue-Eye. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Delicate Blue-Eye need?
Delicate Blue-Eye thrives in brackish tolerant conditions with a temperature range of 25–32°C, a pH between 5 and 7.5, and a general hardness of 5–15 dGH. A moderate water flow is preferred.
Is Delicate Blue-Eye peaceful or aggressive?
Delicate Blue-Eye is classified as peaceful with an aggression score of 1 out of 10. They are generally well-suited to peaceful community tanks.
How many Delicate Blue-Eye should be kept together?
Delicate 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 Delicate Blue-Eye have any special tank requirements?
Yes. Delicate Blue-Eye benefits from plants - densely covered and plants - floating in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Delicate Blue-Eye need a lid on the tank?
Yes. Delicate 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.
Top Tank Mates for Delicate Blue-Eye
These fish are strong compatibility matches for Delicate Blue-Eye based on water preferences, temperament, adult size, and tank behavior.
Emerald Green Cory
Corydoras splendens
Ideal Tank MatesAngelicus Botia
Botia kubotai
Ideal Tank MatesGolden Bristlenose Pleco
Ancistrus sp. L144
Ideal Tank MatesAgassiz Cory
Corydoras agassizii
Ideal Tank MatesAsher Cory
Corydoras tukano
Ideal Tank MatesPanda Garra
Garra flavatra
Ideal Tank MatesPlants That Suit Delicate Blue-Eye
These plants pair well with Delicate Blue-Eye based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Afzel's Anubias
Anubias afzelii
Amazon Sword
Echinodorus amazonicus
Anacharis
Egeria densa
Anubias Barteri
Anubias barteri
Baby Tears
Lindernia rotundifolia
Balansae
Cryptocoryne crispatula
Fish Similar to Delicate Blue-Eye
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.
Forktail Blue-eye
Pseudomugil furcatus
A highly active, nano shoaling fish native to Papua New Guinea. Recognized by their striking blue eyes and energetic swimming patterns. They are peaceful but require open horizontal swimming space and the company of their own kind to thrive. Due to their short lifespan (2-3 years), they mature quickly and display near-constant courtship behavior.
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.
Blue Rainbowfish
Melanotaenia caerulea
A small, highly active, and colorful schooling fish native to the Kikori River system in Papua New Guinea. They are peaceful but require ample swimming space and a school of their own kind to thrive. Like most rainbowfish, they appreciate well-oxygenated, flowing water and are excellent jumpers. Males develop a striking blue hue with reddish horizontal stripes.
Threadfin Rainbowfish
Iriatherina werneri
A delicate and exquisitely shaped nano rainbowfish native to New Guinea and Northern Australia. They are famous for the males' long, filamentous fins and butterfly-like display behavior. Due to their incredibly small throats, they require micro-foods. They are shoaling fish that are easily intimidated by boisterous tank mates.
Dwarf Gourami
Trichogaster lalius
A peaceful to semi-aggressive labyrinth fish native to South Asia. Famous for their brilliant metallic blue and red stripes. While generally suitable for community tanks, males are territorial toward each other and similar-looking fish. They are sensitive to water quality and prone to Iridovirus if stressed. Requires access to the surface to breathe.