Last Updated: October 17, 2026
Ocellaris clownfish (Amphiprion ocellaris) are hardy saltwater fish that do well in a mature marine tank of about 20 gallons (75 litres) for a bonded pair, with water at roughly 24 to 27 C, specific gravity near 1.024 to 1.025 (sources allow about 1.020 to 1.026), pH 8.0 to 8.4 and zero ammonia and nitrite. They do not need an anemone to be healthy, they are usually kept as a pair rather than a group, and captive-bred fish commonly live around 6 to 12 years, with longer reports. A bonded pair is more comfortable in 30 gallons. They are among the easiest marine fish to keep, but “easy” still means a cycled tank, stable salinity and a patient introduction.
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Ocellaris Clownfish Quick Facts
| Trait | Detail |
|---|---|
| Adult size | About 7.5 to 11 cm (3 to 4.5 in); females larger |
| Minimum tank for a pair | About 20 gallons (75 L) is the commonly cited floor; 30 gallons (about 115 L) or more gives more margin, and some sources advise it for a pair |
| Temperature | Roughly 24 to 27 C (75 to 81 F) is the usual target; sources give about 22 to 28 C overall |
| Salinity | Specific gravity about 1.020 to 1.026 across sources; most keepers aim for 1.024 to 1.025 (roughly 32 to 35 ppt) |
| pH / alkalinity | pH 8.0 to 8.4; alkalinity commonly 8 to 12 dKH |
| Nitrate | Low; under 20 mg/L is a common target in fish-only tanks, lower in reefs |
| Diet | Omnivore: pellets, flakes, frozen mysis, brine shrimp, some algae |
| Lifespan | Sources vary: commonly 6 to 12 years in captivity, with reports of 15 to 20 years in stable systems |
| Temperament | Semi-aggressive toward its own species and anything entering its territory |
| Care level | Beginner-friendly for marine fish |
True Ocellaris vs Percula
Ocellaris (Amphiprion ocellaris) and the true percula (Amphiprion percula) are close relatives and are often confused. Both are orange with three white bars edged in black. The percula usually has thicker black edging on the white bars, is a little smaller (about 3 in versus over 4 in for ocellaris) and typically has 10 dorsal-fin spines against 11 for the ocellaris, though counts overlap in some fish and colour and edging vary, so shop labels alone are not reliable. The “common clownfish” sold in most stores is typically ocellaris, and many fish sold as percula are in fact ocellaris.
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Included for 'Ocellaris Clownfish Care: Tank Size, Anemones, Diet and Tank Mates' because the listing specifies 1.76 oz (50g), details this guide uses to compare options.
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Ocean Nutrition Formula Two Pellets - Fish Food for Herbivorous & Omnivorous Marine Tropical Fish, High Protein(40%) - 14 oz (400 g) Medium Pellets
Included for 'Ocellaris Clownfish Care: Tank Size, Anemones, Diet and Tank Mates' because the listing specifies Fish Food for Herbivorous & Omnivorous Marine Tropical Fish and High Protein(40%), details this guide uses to compare options.
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Omega One Garlic Marine Small Sinking Pellets, 4.5 oz.
Included for 'Ocellaris Clownfish Care: Tank Size, Anemones, Diet and Tank Mates' because the listing specifies 4.5 oz., details this guide uses to compare options.
View on AmazonThe two behave very similarly, and the tank size, feeding and water targets in this guide apply to both. The practical difference is minor: both are described as hardy when captive-bred, and one retailer guide suggests a slightly larger tank for the percula (30 gallons rather than 20). Designer morphs of the ocellaris, such as black, snowflake, wide-band or picasso patterns, are bred in captivity and have the same care needs as the wild type.
Tank Size and Setup
Some keepers house a single ocellaris in a 10-gallon nano tank, though many sources suggest 20 gallons even for one fish. For a pair, a 20-gallon tank is the commonly cited floor, and 30 gallons or more is more forgiving. Bigger water volume buffers swings in salinity and temperature, which are the main killers of small marine tanks.
Footprint and swimming space
Clownfish are not long-distance swimmers. They hover around a host, rock or powerhead and dart out for food. A footprint of at least 60 cm (24 in) long gives the pair a territory and room for tank mates to avoid it. Height matters less. Rockwork should have a few overhangs and a cleared area at the base so the pair has a place to claim.
Equipment checklist
- A heater and a separate thermometer, so a stuck heater is caught.
- A protein skimmer or generous filtration with live rock; both help keep nutrients down.
- Powerheads or a return pump for moderate flow; clownfish do not like extremely strong current.
- A refractometer, which reads salinity more accurately than a swing-arm hydrometer, and test kits for ammonia, nitrite, nitrate, alkalinity and pH.
- A covered or low-water-level tank, since clownfish can jump when startled.
- An auto top-off or a routine of adding fresh water to replace evaporation. Salt does not evaporate, so topping up with saltwater makes the tank saltier over time.
Cycling
Clownfish are tough, but a new tank needs to be fully cycled before any fish go in. Ammonia and nitrite should read zero for several days with the rock in place. Buying fish too soon is the most common reason for early losses.
Water Parameters
- Salinity: sources give slightly different specific gravity windows between 1.020 and 1.026. A steady 1.024 to 1.025 sits inside nearly all of them. Stability matters more than the precise number.
- Temperature: 24 to 27 C is the main band, with some sources allowing about 22 to 28 C.
- pH: 8.0 to 8.4.
- Alkalinity: 8 to 12 dKH, important mainly for reef tanks.
- Ammonia and nitrite: zero.
- Nitrate: under 20 mg/L for fish-only; lower for corals.
Partial water changes of roughly 10 to 20 percent every one to two weeks are enough for most lightly stocked tanks.
Anemone or No Anemone?
In the wild, ocellaris live among host anemones, mainly Heteractis magnifica, Stichodactyla gigantea and Stichodactyla mertensii. In aquariums, tank-bred ocellaris frequently never use an anemone, and many keepers report they host corals, powerheads, or simply a rock corner instead. They are healthy without one.
Anemones are far harder to keep than the fish. They need mature tanks, strong stable lighting, excellent water quality and, according to many keepers, a larger system than a clownfish pair alone. They can sting other livestock, wander into powerheads and die suddenly, fouling the tank. A responsible approach is to keep the fish first, wait until the tank has been stable for 6 to 12 months, and consider an anemone only if the lighting and tank suit it. Wild-collected anemones also carry a conservation and sourcing question.
| Decision | Pick this if… |
|---|---|
| No anemone | Smaller or newer tank, beginner, or you want the simplest care |
| Captive-bred anemone | Mature reef, strong stable lighting, larger tank, patient with water quality |
| Substitute host (coral, rock, powerhead) | You want the hosting behaviour without anemone risk; the fish will pick for themselves |
Pair Formation and Aggression
All clownfish are born male, and the dominant fish in a group changes sex to female. A pair therefore forms by a simple route: introduce two juveniles of different sizes, and the larger becomes the female. A group of three or more may work in a big tank, but in small tanks two females will fight, sometimes to the death.
- Buy two juveniles together, ideally of different size, rather than adding a second adult later.
- If adding a second fish to an existing one, choose a noticeably smaller juvenile and use a tank divider or rearrange rockwork first, so territory is reset.
- Expect lots of shimmying, chasing and head-bobbing during the first week. Constant, bloody attacks mean separation.
- Do not keep more than one pair in a small tank.
Established pairs may lay eggs on a cleaned flat surface, guarded by the male. Eggs are fertile when the pair is healthy; raising fry requires a dedicated setup with rotifers and special culture work.
Feeding
Ocellaris will eat nearly anything. A varied diet of marine pellets or flakes, frozen mysis and brine shrimp, and the occasional nori sheet supports growth and colour.
- Feed small portions once or twice a day, only what is eaten in two minutes.
- Alternate pellets with frozen foods and add vitamin-enriched food several times a week.
- Soak dry food briefly before feeding to reduce bloating.
- Remove uneaten food, which fuels algae and nitrate.
Tank Mates
Clownfish are best kept in peaceful communities. They defend their patch, so avoid adding a more aggressive or similar-looking fish. Add them early or late in the stocking order based on temperament: many keepers add clownfish last in small tanks, since an established fish can claim the whole space.
| Group | Examples | Notes |
|---|---|---|
| Good | Firefish and other gobies, royal grammas, cardinalfish, small wrasses such as fairy wrasses, blennies, cleaner shrimp, snails and hermit crabs in a reef | Peaceful and similar in size, with different territory |
| Risky | Other clownfish species, dottybacks, tangs in small tanks, large hawkfish | Territorial overlap or fighting over space |
| Avoid | Triggerfish, groupers, lionfish, large angelfish, aggressive damselfish | Predators or bullies that can injure or eat the clownfish |
Reef-safe corals are generally fine, though clownfish may nip or shelter in soft corals and large polyp stony corals.
Tank-Bred vs Wild-Caught
Captive-bred ocellaris are the better choice. They are accustomed to prepared foods, usually hardier, and spare wild reefs. Sources describe cyanide and rough collection damaging wild fish in some regions, and wild fish often struggle to adapt. Captive-bred stock is now common and tends to lose fewer fish after purchase. Ask the seller whether the fish was captive-bred, whether it is eating, and how long it has been in the shop tank.
Common Problems and Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| White salt-like spots | Marine ich (Cryptocaryon) | Quarantine and treat in a separate tank; reef-safe approaches differ from fish-only |
| Brooklynella: slimy white coating, rapid breathing | Brooklynella (clownfish disease) | Move to a hospital tank, freshwater dips and approved treatment; act fast |
| Gasping, clamped fins | Poor water, low oxygen, ammonia | Test and change water; increase surface agitation |
| Torn fins or missing scales | Pair fighting or aggressive tank mate | Separate fish; rearrange rockwork; reduce stocking |
| Loss of colour | Stress, poor diet, water drift | Check salinity and temperature; improve diet |
| Refusing food | New environment, illness | Offer frozen mysis; check water; observe for disease |
Weekly Maintenance Schedule
- Daily: feed, check temperature, top off evaporated water with fresh water, look for white spots or damage.
- Weekly: test salinity, ammonia, nitrite, nitrate; change 10 to 20 percent of water; empty the skimmer cup; clean glass.
- Every two weeks: test alkalinity and pH; rinse filter media in used tank water.
- Monthly: clean pumps and powerheads, check heater and thermometer.
Common Mistakes
- Adding fish to a new, uncycled tank.
- Letting salinity drift upward by topping up with saltwater.
- Putting two adult females together.
- Chasing anemones too early.
- Skipping quarantine for new fish and introducing disease.
- Overfeeding and letting nitrate climb.
Frequently Asked Questions
Do ocellaris clownfish need an anemone?
No. Tank-bred ocellaris often never host an anemone and stay healthy. Anemones are more demanding than the fish and need a mature, well-lit tank.
What size tank do two ocellaris clownfish need?
About 20 gallons is the commonly cited minimum for a pair, though some sources advise 30 gallons, and larger is safer. Larger volume keeps water more stable and gives other fish room.
What is the difference between ocellaris and percula?
They are closely related and look similar. Percula tend to have thicker black outlines on the white bars, a little smaller adult size and usually 10 rather than 11 dorsal spines, but trade names are unreliable. Care for both is essentially the same.
Can I keep three clownfish together?
It is possible in a large tank, but in smaller systems the third fish is often bullied. A single pair is the more reliable arrangement.
How long do ocellaris clownfish live?
Sources vary. Captive-bred fish commonly live around 6 to 12 years with stable conditions, and some keepers report 15 to 20 years. Treat them as a long-term commitment of a decade or more.
What do ocellaris clownfish eat?
They eat pellets, flakes, frozen mysis and brine shrimp, and some algae. A mix of foods once or twice daily is enough.
Can ocellaris live in a reef tank?
Yes, they are generally reef-safe. They may nestle in soft corals or bubble-tip anemones, and they do not usually eat corals.
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