Saltwater Fish · Clownfish
Maroon Clownfish
Amphiprion biaculeatus
Large, boldly coloured and notably aggressive clownfishIntermediate
- Lifespan
- 10-15 years
- Size
- 6-7 in15-17 cm female
- Social needs
- Solitary or one bonded pair only
- Time
- Daily feeding; weekly testing/changes
- Cost
- High
- Diet
- Omnivore (meaty frozen, pellets, algae)
Overview
What is this animal?
- The Maroon is the largest and most aggressive clownfish, with deep maroon-red colour and white or gold stripes.
- The female grows much larger than the male and dominates the pair.
- It is hardy and long-lived, but its temperament makes it unsuitable for peaceful community tanks.
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- Note that the former genus Premnas was merged into Amphiprion in 2021, so older sources list it as Premnas biaculeatus.
- With this clownfish, size and attitude matter.
- A large female harasses tankmates, nips hands during maintenance, and bullies smaller fish.
- Choose it for its appearance only if you can give it space and select tankmates carefully.
Temperament
- The Maroon is the most belligerent clownfish, with females in particular defending a large territory and bullying tankmates and even the aquarist's hand.
- It is reef-safe with corals but a threat to small, peaceful fish.
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- Keep a single fish or one young bonded pair only; never mix it with other clownfish species.
- Because of its size and aggression it suits a larger, carefully stocked tank where calmer or similarly bold tankmates can hold their own.
A good fit for
- Keepers wanting a large, bold clownfish
- Larger reef or FOWLR tanks
- Aquarists who can manage aggression
- Single-specimen or bonded-pair setups
Common mistakes to avoid
- Underestimating adult size and aggression
- Mixing with other clownfish species
- Keeping two unbonded adults together
- Too-small tank causing constant bullying
Enclosure
Minimum 79 gallons300 litres
Fine alone or with company. Solitary or one bonded pair only
- Provide at least 80 gal300 L, in a tank at least 39 in100 cm from end to end, for the adult size and territorial range, with robust live rock structure.
- Keep salinity 1.024-1.026, temperature 75-80°F24-27°C, pH 8.1-8.4, and nitrate below 20 ppm in a fully cycled system.
- A secure lid prevents jumping.
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- Introduce a true bonded pair while young, or keep a single fish, since unbonded adults fight viciously.
- Add the Maroon last so it cannot claim the whole tank before tankmates settle.
- Strong, stable conditions keep this large clownfish healthy long-term.
Supplies
Setup
- Tank, stand and sump, about 80-90 US gallons300-340 litres
- Return pump and powerheads
- Protein skimmer
- Reef lighting
- Rock and sand
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- Salt mix, refractometer and test kits
- Quarantine tank
Ongoing
- Quality small marine pellet
- Frozen mysis shrimp
- Frozen enriched brine shrimp
- Algae-based marine flake
- Vitamin or HUFA soaking supplement
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- Small thawing cup and strainer
- Turkey baster for target-feeding
Safe substrate: Aragonite sand · Dry or cured live rock
Care routine
Daily
- Check salinity, temperature and flow
- Feed small marine portions
- Head-count and look everyone over
- Top up evaporation with fresh water
Every few days
- Service the skimmer and filter socksevery 3 days
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Weekly
- Clean the glass
- Test the water
- Watch the pair's pecking order
- Water change
Monthly
- Calibrate the refractometer
- Check salt, RO/DI and reagents
Less often
- Deep-clean pumps and powerheadsevery 3 months
- Replace RO/DI filter mediaevery 6 months
Health review: Quarterly review with a pair check, every 3 months
Tools
Care in depth
Diet
Omnivore (meaty frozen, pellets, algae)
- Maroons are hearty omnivores.
- Feed a marine pellet staple plus meaty frozen foods such as mysis and chopped seafood, with some algae-based food for balance.
- Adults have big appetites, so feed once or twice daily without overfeeding the tank.
- They accept prepared foods readily, especially captive-bred specimens.
- A varied diet supports their colour and immune strength.
- Soak frozen foods in vitamins occasionally and do not let uneaten food foul the water.
Health
Signs of good health, and the common problems
- Like all clownfish they are prone to marine ich and Brooklynella when stressed, but their hardiness makes serious illness uncommon in stable water.
- Quarantine new fish and keep salinity and temperature steady to avoid outbreaks.
- Watch for scratching, white spots, or laboured breathing.
- Their aggression can also injure tankmates, so monitor other fish for fin damage rather than the robust Maroon itself.
- Good husbandry keeps them healthy for well over a decade.
Is this urgent?
6 warning signs and how fast to act, 3 of them right away
In a reef, stability matters more than any single target number. A parameter moving fast does more damage than a parameter sitting slightly off.
Go now
Any detectable ammonia or nitriteWater change now with matched, mixed and aerated saltwater. Stop feeding. Ammonia is directly toxic, and at reef pH more of it is in the toxic form, so a marine system has less margin than a freshwater one. Nitrite is far less toxic in seawater, but any reading in a stocked tank means the biological filter is not keeping up.
NowTemperature or salinity has moved sharplyCorrect slowly, over hours, not minutes. Check the heater and the top-off. The speed of the change does the damage. Correcting fast repeats the injury in the other direction.
NowRapid gilling, or a fish hanging in the flow breathing hardIncrease aeration and check temperature and salinity. Warm water holds less oxygen, and a heater failure shows up here first.
NowToday
White spots, or a fine dusting like icing sugarIdentify which parasite before treating. Most reef tanks cannot be treated in place. The two common parasites look similar and need different handling; velvet can kill a tank in days.
TodayCorals closed for more than a day, or receding tissueTest alkalinity first, and compare it against the last reading rather than a target. Unstable alkalinity is the most commonly cited coral killer, and a swing shows up in the trend, never in a single point.
TodayA new fish added without quarantine now looks unwellRemove it to a separate system today if you can. Nearly every wipeout in a reef tank traces back to a skipped quarantine.
TodayQuarantine every new animal, including corals and inverts. It is the single practice that separates a reef that lasts from a reef that restarts.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it, and the time to find one is before you need one.
Bedding and substrate
2 safe, 3 with a caveat, 2 to avoid
In a marine system the rock and the sand are life support, and how you start them decides the first six months.
Safe
Aragonite sandThe standard marine substrate, and it hosts the biology. It does not meaningfully hold pH or alkalinity at normal reef pH, so test and dose for those regardless.
safeDry or cured live rockDry rock avoids importing pests but takes longer to mature. Cured rock is faster and riskier.
safeWith a caveat
Deep sand bedsPowerful nutrient processing when they work and a sulphide release when they are disturbed. Choose shallow or deep deliberately, not by accident. A sand-sifting or burrowing goby needs a fine bed about 2 to 3 in5 to 8 cm deep that it turns over itself. That is a different thing from a denitrifying deep sand bed (4 in10 cm or more, left undisturbed), and the two do not mix: a sifting goby disturbs the layers a deep sand bed depends on and eats the life in it.
with a caveatUncured live rockIt will cycle the tank for you, and it will also bring in whatever was living in it.
with a caveatBare bottomWorkable in high-flow systems for fish that neither sift nor burrow, but it removes a large part of the biological buffer. Wrong for watchman gobies and other gobies that burrow or sift, which need a fine sand bed at least 2 in5 cm deep to dig and feed in, and for mandarins and other copepod-eaters, which need sand as well as mature rock for their food to breed in.
with a caveatNever
Silica play sandNot the marine standard, and commonly blamed for feeding diatom blooms in a new tank.
neverAny rock or decor of unknown originMetals and phosphate leach for months and are almost impossible to trace once the tank is running.
neverThis is our general list for saltwater fish. We have not built one specific to Clownfish yet.
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-10-22.
YouTubers
HumbleFish & ReefSaltwater fish disease, quarantine and treatment (Humble.Fish forum)BRStvReef tank setup, fish health and quarantine series (run by a retailer)FishOfHex AquaticsBeginner saltwater guides, avoiding common mistakes and tank disasters
Sites
Keep going
Clownfish, side by side
Same axes, same care guides: the honest way to choose between types.
