Can monos be kept in freshwater?

Monos are naturally found in estuaries and mangrove habitats, so they should be kept in brackish water as a rule. Long-term keeping in plain freshwater isn't recommended, and salinity needs to be managed.

How many should be kept together?

They show their natural, beautiful schooling behavior best when kept in groups rather than alone. Be sure to plan tank space for their adult size based on how many you keep.

How big do monos eventually get?

Adults range from 12 to 27cm, varying by individual and rearing conditions. It's important to choose a tank with their eventual size in mind.

How difficult are monos to keep?

Monos are classified as suited to intermediate keepers. Some prior experience managing brackish conditions helps achieve more stable, consistent care.

Is this species subject to any regulation?

The mono is not subject to CITES.

Mono

The mono, or Monodactylus, is a brackish-water fish native to estuaries and mangrove habitats across the Indo-West Pacific, easily recognized by its silvery, diamond-shaped body and two bold black bars crossing the eye and gill cover. It's a schooling species, and keeping several together really brings out its natural charm as they move through the water in unison. Growing up to 27cm, it needs plenty of swimming room as it matures, but its active, hardy nature and captivating group behavior have made it a longtime favorite among enthusiasts. Classified as suited to intermediate keepers, it's a good match for those already comfortable managing brackish conditions.

View Mono encyclopedia →

Find Mono breeders(0)

Limited Time Offer

0% commission on your first sales!Register by September 30, 2026 and your first 2 sales are commission-free!

Breeder Wanted!

List on BreederDirect and sell directly to customers nationwide!

Free registrationNo monthly feesCommission on sales only

Our 6 Transparency Commitments

All Tropical Fish listings include water quality, temperament, and tank size information from verified Breeder.

Origin Disclosed
Real Photos
Water Quality Disclosed
Recommended Tank Size
Temperament Disclosed
Breed Line Disclosed

All species Guppy Endler's Livebearer Betta Peaceful Betta Emerald Betta Brunei Beauty Discus Pleco Otocinclus Bristlenose Pleco Zebra Pleco Otocinclus Negro

Browse all 301 breeds

Filter

Price

Region

Has show resultsChampion titles

Attributes

WYSIWYG (Actual photo)

0 items

Sort by

Verified breeders wanted for Tropical Fish

Breeders are signing up now ahead of launch. Subscribe to be notified when new listings go live.

Find breeders Browse the Tropical Fish encyclopedia

Getting alerts is free with a member account. When new listings match your saved search, we'll notify you by email and in-app.

Browse other categories

Dogs Cats Marine Fish Coral Goldfish Medaka Reptiles & Amphibians Small Pets Birds Insects Exotic Invertebrates

Verified breeders (preview)

中

中村篤史 Breeder

大阪府

西

西川康弘 Breeder

香川県

Are you raising tropical fish?

Apply as a breeder

Mono key facts

Care level: Intermediate
Lifespan: 5-8 years
Size: 12-27cm
Temperature: 22〜26℃
Diet: Prepared foods with both animal and vegetable content, frozen foods
Tank: LiveAquaria gives a 492 litre (130 gallon) minimum. It is a strong swimmer, so choose a long tank and leave plenty of open water.
Water Temperature & Quality: LiveAquaria gives 22-26C (72-78F), pH 8.1-8.4 and 8-12dKH; FishBase records 24-28C in the wild. It tolerates a wide salinity range from brackish to marine, but long-term keeping calls for a stable salinity and a high, steady pH.
Tank Mates: LiveAquaria rates it semi-aggressive, and it is known to show territorial behaviour, though it may stay solitary or school. Pair it with robust brackish fishes of similar size.
Diet & Feeding: An omnivore feeding on detritus and plankton in the wild. Offer prepared foods containing both animal and vegetable matter, supplemented with frozen foods.
Breeding & Spawning: Home-aquarium breeding is rarely recorded, so the focus of keeping is long-term care in stable brackish to marine water.
Health & Notes: This is a brackish to marine fish and should not be kept permanently in fresh water. Juveniles handle salinity changes well, but any change should still be made gradually.

TraitsBrackishFreshwater fishMedium speciesShoaling

About Mono

The mono is a brackish-water fish with a silvery, diamond-shaped body and two black bars. It schools beautifully and grows up to 27cm, suited to intermediate keepers.

7 things to know before welcoming a Mono

1Requires Brackish Water
Monos come from estuaries and mangrove habitats, so they aren't suited to long-term life in plain freshwater. Use a hydrometer to monitor salinity and avoid sudden changes in water chemistry.
2Best Kept in Groups
Their natural beauty really shows when several are kept together rather than alone. A solitary mono can seem restless, so it's worth considering introducing multiple individuals if space allows.
3Plan for Adult Size
Adults range from 12 to 27cm, so if you're keeping a group, it's important to plan for a larger tank down the line. Even if they're small when you bring them home, plan your setup with their eventual size in mind.
4Active Swimmers
Monos are highly active swimmers that move around the tank energetically. Unlike species that prefer to hide, they favor open space, so it's best to design the layout with plenty of clear swimming area.
5Choosing Tankmates
Tankmates need to be species that can also thrive in brackish conditions. Before adding companions, check whether they can comfortably tolerate the same brackish setup.
6Stable Water Quality Matters
They can be sensitive to abrupt shifts in water quality or salinity. Regular water changes paired with routine salinity checks help maintain the stable environment they need to stay healthy.
7Prepare Equipment in Advance
Having marine salt mix and a hydrometer ready in advance makes setup much smoother. Establishing the brackish environment from the tank cycling stage helps avoid a scramble once your monos arrive.

Frequently asked questions about Mono

Q.Can monos be kept in freshwater?: A.Monos are naturally found in estuaries and mangrove habitats, so they should be kept in brackish water as a rule. Long-term keeping in plain freshwater isn't recommended, and salinity needs to be managed.
Q.How many should be kept together?: A.They show their natural, beautiful schooling behavior best when kept in groups rather than alone. Be sure to plan tank space for their adult size based on how many you keep.
Q.How big do monos eventually get?: A.Adults range from 12 to 27cm, varying by individual and rearing conditions. It's important to choose a tank with their eventual size in mind.
Q.How difficult are monos to keep?: A.Monos are classified as suited to intermediate keepers. Some prior experience managing brackish conditions helps achieve more stable, consistent care.
Q.Is this species subject to any regulation?: A.The mono is not subject to CITES.

Useful tools for Mono care

💧Aquarium Volume CalculatorCalculate water volume, weight, and heater wattage from tank dimensions 🧪Water Quality CheckerFind compatible fish, shrimp, plants & corals based on pH, temperature & hardness 🍽️Feeding GuideCheck feeding frequency, portion sizes & supplements by species and growth stage 🤝Compatibility CheckerCheck compatibility between two species on a 5-level scale 📊Fish Compatibility MatrixCheck fish compatibility at a glance with our matrix chart 🔄Nitrogen Cycle GuideAuto-calculate bacteria colonization timeline for new tank cycling 🗓️Seasonal Care CalendarMonthly care events and seasonal management tips at a glance 🚿Water Change CalculatorAuto-calculate optimal water change frequency and volume by tank size and fish count 🐠Stocking CalculatorCalculate max fish capacity for your tank size with overstocking alerts ⚡Electricity Cost SimulatorCalculate monthly and annual electricity costs for care equipment with presets 🧬Breeding PlannerSelect parent varieties to view breeding schedules and offspring patterns 🏞️Tank Layout PlannerGet substrate, plant & hardscape suggestions based on tank size and style 🧮Care Cost SimulatorEstimate initial, monthly & annual costs by category, care level and quantity ⚖️Species Comparison ToolCompare two species side by side: care difficulty, size, lifespan & temperature 🎯Pet Match DiagnosticAnswer 7 questions to find your top 3 perfect pets 📋Lifetime Cost SimulatorEstimate lifespan and lifetime costs by species for dogs, cats, reptiles and more 🚚Transport Safety CheckerCheck transport safety score and precautions by category, season, method and distance 💊Medication Dosage CalculatorCalculate proper medication dosage by body weight and medicine type for fish, reptiles, and small animals ⏱️Quarantine & Acclimation TimerManage quarantine periods and acclimation steps with countdown timers. Includes recommended durations by species

Learn more about Mono in the encyclopedia

View Mono encyclopedia entry →

Care difficulty, lifespan, size and diet — all basics covered.

Mono related articles

Complete Guide to Setting Up a Brackish Water Aquarium | Salinity and Care for Bumble Bee Goby and Monodactylus

How to care for Bumble Bee Gobies, Monodactylus, and other fish that live in brackish (intermediate between freshwater and saltwater) environments. Detailed explanation of salinity settings, suitable fish species, and water quality management methods.

Peacock Bass (Cichlid) Care Guide | Species, Equipment, Legal Regulations, Breeding

A comprehensive guide to caring for Peacock Bass (Cichla genus), large carnivorous cichlids native to South America. Compare key species including Monoculus, Temensis, and Ocellaris; understand Japan's legal regulations (release strictly prohibited); set up large aquariums (150cm+); learn feeding transitions to artificial diets; manage mixed-species tanks with large fish; and explore breeding highlights where you can observe spawning bed construction. A complete guide for responsible keeping.

See more Mono articles →