Common name
African moony
Scientific name
Monodactylus sebae
Category
Brackish fish
Group
Moonies and brackish schooling fish
Environment
Brackish to marine aquarium
Origin
Eastern Atlantic coast from Cape Verde and Senegal to Angola, including estuaries, lagoons, river mouths, shallow bays and harbours
Care level
Advanced
Adult size
Up to 25 cm total length
Expected lifespan
Plan for 10–15 years; this is a long-lived large shoaling commitment rather than a temporary juvenile freshwater display.
Minimum housing
At least 800 L with a 200 cm or longer swimming length for six or more adults
Temperature
24–28 °C
pH
7.5–8.5
Hardness / minerals
Alkalinity 7–12 dKH; maintain calcium and magnesium appropriate to the chosen brackish or marine salinity
Salinity
Euryhaline, but adults should not be kept permanently in freshwater; maintain a stable brackish-to-marine system, commonly about 15–35 ppt
Lighting
Moderate, with open swimming space and some shaded refuge
Placement / zone
Middle and upper open water
Filtration
Use mature biological filtration sized for the complete adult african moony group, with guarded intakes and accessible mechanical capture. Keep flow strong enough for a large active shoal without creating uncontrolled salinity gradients where the fish lives, and maintain undetectable ammonia and nitrite.
Aeration
Maintain reliable surface agitation and oxygen exchange at all times. Increase aeration during warm weather, medication, transport recovery, heavy feeding or any sign of rapid breathing.
Maintenance
Perform regular matched-water changes guided by nitrate and waste, remove uneaten food and trapped detritus, clean mechanical media without disrupting the biofilter, and record feeding, body condition, respiration and aggression.

Identity and search names

Single-species profile for Monodactylus sebae. Preserve permanent AquaNexus ID 15, slug african-moony and route species/african-moony/index.html; retain former combinations, locality labels and trade names only as searchable aliases.

Search names: African mono, West African moony

Environment and housing

Very large open brackish-to-marine aquarium with powerful filtration, vigorous gas exchange, secure cover and stable measured salinity

Social structure: Keep at least six; smaller groups concentrate hierarchy and chronic chasing

Feeding and nutrition

Feeding ecology: Fish, shrimp, zooplankton and other small invertebrates; accepts varied marine or brackish prepared foods

Feeding routine: Feed two or three measured meals daily and maintain body condition without overloading filtration

Breeding, reproduction or spread

Marine or estuarine open-water spawning is documented; home propagation remains specialist and no brood care follows spawning

Detailed care and app-ready planning

Identity scope
Single-species profile for Monodactylus sebae. Preserve permanent AquaNexus ID 15, slug african-moony and route species/african-moony/index.html; retain former combinations, locality labels and trade names only as searchable aliases.
Adult size and space
Expected adult size: Up to 25 cm total length. Minimum permanent housing: At least 800 L with a 200 cm or longer swimming length for six or more adults. Plan around adult dimensions, activity, social structure, aggression, oxygen demand and waste production rather than sale size.
Social structure
Keep at least six; smaller groups concentrate hierarchy and chronic chasing
Swimming zone or placement
Primary zone: Middle and upper open water. Keep that zone usable for movement, feeding, refuge and escape.
Feeding ecology
Fish, shrimp, zooplankton and other small invertebrates; accepts varied marine or brackish prepared foods
Feeding plan
Feed two or three measured meals daily and maintain body condition without overloading filtration
Water stability
Maintain 24–28 °C; pH 7.5–8.5; hardness or minerals: Alkalinity 7–12 dKH; maintain calcium and magnesium appropriate to the chosen brackish or marine salinity; salinity: Euryhaline, but adults should not be kept permanently in freshwater; maintain a stable brackish-to-marine system, commonly about 15–35 ppt. Stable oxygenation and nitrogen-cycle control matter more than chasing one exact value.
Habitat structure
Very large open brackish-to-marine aquarium with powerful filtration, vigorous gas exchange, secure cover and stable measured salinity
Compatibility plan
Only with similarly robust brackish or marine fish that tolerate the same salinity and cannot be swallowed
Breeding or reproduction plan
Marine or estuarine open-water spawning is documented; home propagation remains specialist and no brood care follows spawning Parental care: None after spawning.
Quarantine
Quarantine new livestock in a separate cycled system for at least 30 days. Observe appetite, respiration, waste, skin, fins and behaviour; use dedicated equipment and never add transport water to the established aquarium.
Welfare checks
Maintain the stated adult space and social structure, verify feeding, and intervene early when injury, exclusion, weight loss, abnormal respiration or altered behaviour appears. Freshwater juveniles are often sold without the adult commitment being explained. A 25 cm shoal requires a very large stable brackish-to-marine system.
Biosecurity and release
Never release fish, fry, eggs, aquarium water, sediment, plants or live foods into drains, dams or natural waterways. Confirm current Australian import conditions and South Australian possession, trade and movement rules before acquisition or transfer.
Main risk
Freshwater juveniles are often sold without the adult commitment being explained. A 25 cm shoal requires a very large stable brackish-to-marine system.
Adult projected load
Project biological load from the full adult african moony group, adult body mass, feeding pattern, activity and social requirement rather than juvenile sale size. Six or more 25 cm adults in brackish-to-marine water create a very high oxygen, feeding and solids load.
Filtration
Use mature biological filtration sized for the complete adult african moony group, with guarded intakes and accessible mechanical capture. Keep flow strong enough for a large active shoal without creating uncontrolled salinity gradients where the fish lives, and maintain undetectable ammonia and nitrite.
Aeration
Maintain reliable surface agitation and oxygen exchange at all times. Increase aeration during warm weather, medication, transport recovery, heavy feeding or any sign of rapid breathing.
Maintenance
Perform regular matched-water changes guided by nitrate and waste, remove uneaten food and trapped detritus, clean mechanical media without disrupting the biofilter, and record feeding, body condition, respiration and aggression.
Overridable warnings
Non-overridable: do not accept persistent ammonia or nitrite, oxygen distress, starvation, chronic aggression or inadequate adult space. Different equipment, stocking or maintenance methods may be used only when measured water quality and adult welfare remain equivalent or better. Adults must not be stranded in freshwater, and the full shoal requires the stated long swimming footprint.

Compatibility, welfare and risk

Compatibility: Only with similarly robust brackish or marine fish that tolerate the same salinity and cannot be swallowed

Welfare: Maintain the stated adult space and social structure, verify feeding, and intervene early when injury, exclusion, weight loss, abnormal respiration or altered behaviour appears. Freshwater juveniles are often sold without the adult commitment being explained. A 25 cm shoal requires a very large stable brackish-to-marine system.

Main warning: Freshwater juveniles are often sold without the adult commitment being explained. A 25 cm shoal requires a very large stable brackish-to-marine system.

Biosecurity and release

Never release fish, fry, eggs, aquarium water, sediment, plants or live foods into drains, dams or natural waterways. Confirm current Australian import conditions and South Australian possession, trade and movement rules before acquisition or transfer.

Sources