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Care guide · Freshwater · fish

Pacific blue-eye

Pseudomugil signifer

Pacific blue-eye (Pseudomugil signifer)
Photo: MurkySeb, CC BY-SA 4.0; resized and compressed. Photo: MurkySeb · Source · CC BY-SA 4.0Resized and compressed; no cropping or colour changes.

The Pacific blue-eye (Pseudomugil signifer) is a small, active blue-eye from coastal eastern Australia. It occurs naturally in freshwater creeks and swamps as well as brackish estuaries; this does not mean aquarium salt is required. Adult males often have longer, more colourful fins and display them during courtship and rivalry. The species is highly variable: northern populations can grow much larger, and males may become strongly territorial when breeding. Ask about locality or captive line and do not casually mix origins. A group of at least eight, a mature aquarium with adequate swimming room and fine varied food matter more than copying every natural salinity.

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At a glance

Temperature
20–26 °C
pH
6.5–7.5
GH
5–15 °dGH
Aquarium length
At least 60 cm
Minimum aquarium volume
At least 54 L
Adult size
Up to 7 cm
Group size
At least 8 individuals
Temperament
Peaceful, Territorial

About this species

The accepted name is Pseudomugil signifer Kner, 1866, family Pseudomugilidae. Older taxonomic names include Atherina signata, Atherinosoma jamesonii, Pseudomugil signata, P. signatus and P. affinis. FishBase and Seriously Fish report up to 7 cm standard length, but that maximum does not describe every population. Body size, colour and fins vary across the broad range. Research and specialists indicate that the current broad species concept may later be divided. Until a formal revision, treat local populations as distinct lines and do not mix northern and southern forms without knowing their origins.

Natural habitat

Its range follows much of Australia’s eastern coast, from Cape York to southern New South Wales. It inhabits freshwater creeks, swamps, forest waters and brackish coastal habitats; some sites are tidal creeks or mangrove estuaries. Natural conditions vary with locality and season. The fish can also be maintained in fully fresh water, including specimens from brackish or marine sites. This is tolerance, not a reason to add salt. Use locality and the needs of any companions to plan a stable aquarium.

Aquarium and layout

Seriously Fish gives a 60 × 30 cm footprint and about 54 litres gross as a minimum to consider for most forms. It warns that large northern populations may need substantially more. Choose a larger tank when origin is unknown or fish are from a large northern form. Keep at least eight, with room for a larger shoal. Use planted margins, wood or roots, floating cover and open surface swimming space. Good oxygenation and gentle to moderate flow suit it. Add fish only to a fully mature aquarium; stable water chemistry matters. A secure lid helps prevent escapes.

Water conditions

For routine freshwater aquarium care, Seriously Fish gives 20–26 °C, pH 6.5–7.5 and GH 5–15 dGH. ANGFA describes a broader natural tolerance of 15–28 °C and pH 5.5–8.3; the lowest temperatures mainly apply to southern populations in winter. Field tolerance is not a reason to let aquarium temperature fluctuate. The species tolerates fresh, brackish and even marine water, but added salt is unnecessary for normal care. Keep conditions stable and consider the population and any companions. No specific KH target was established.

Behaviour and group size

Pacific blue-eyes shoal near the surface and in midwater. Many populations are peaceful, but males court and defend spawning sites. Adult males of large northern forms may seriously injure or kill subordinate males in small tanks. Keep origins separate, avoid crowding and provide space and visual barriers. Choose companions by adult size, temperament, feeding competition, swim zone and water needs; matching temperature alone does not establish compatibility. With uncertain origin, a species-focused aquarium and suitable group is the cautious choice.

Feeding

In nature it consumes zooplankton, phytoplankton and small invertebrates. Offer particles small enough to swallow: finely crushed floating flakes, small Daphnia, brine shrimp, microworms or suitably sized frozen foods. Vary dried food with animal foods and feed several modest portions. Check that subordinate fish also eat. Large pellets may be refused or simply not fit. Remove leftovers to protect water quality, especially in small breeding or quarantine tanks.

Breeding

The species scatters adhesive eggs among aquatic plants or on spawning mops and provides no parental care; adults may eat eggs and fry. Females deposit small numbers over several days. Males defend spawning sites, so very small breeding tanks and isolated pairs can lead to chasing or injury. A group with several spawning areas can spread aggression. Check moss or mops daily and move eggs if raising fry. Incubation varies with temperature; Seriously Fish reports roughly 10–21 days. Keep rearing water clean and feed fry particles they can actually take.

Sources & review

This care guide draws on several specialist sources and was last checked on .

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