Amphiprion clarkii — Clark's Clownfish

Species Overview

Amphiprion clarkii, commonly known as Clark's Clownfish or the Yellowtail Clownfish, is a species of damselfish (family Pomacentridae) native to the Indo-Pacific region, from the Persian Gulf and East Africa to the western Pacific islands, including the Great Barrier Reef, Philippines, and southern Japan. It occupies a wide range of reef habitats, from lagoons to outer reef slopes, typically at depths of 1–55 meters.

Taxonomically, Amphiprion clarkii belongs to the genus Amphiprion—the true clownfishes—and was first described by Edward Turner Bennett in 1830. It is one of the most geographically widespread and morphologically variable clownfish species, exhibiting multiple color morphs depending on locality (e.g., black-bodied in some regions, orange-bodied in others). In the aquarium trade, it is often referred to as the "Clarkii Clown" or "Clark's Anemonefish."

In the hobby, Clark's Clownfish is valued for its hardiness, adaptability, and bold personality. Unlike the more delicate Amphiprion ocellaris, this species tolerates a broader range of water parameters and is less prone to stress-related diseases. It is also one of the few clownfish species that can be kept without a host anemone, often adopting artificial structures or even large-polyp stony corals as surrogate hosts. This makes it an excellent choice for both novice and experienced marine aquarists.

Tank Requirements

Minimum tank size: 30 gallons (114 liters) for a single specimen or a mated pair. For a small group (3–5 individuals), a 55-gallon (208-liter) tank is recommended to reduce aggression.

Substrate: Fine aragonite sand (1–2 mm grain size) is ideal, as it mimics the natural reef environment and helps maintain buffering capacity. Avoid coarse gravel, which can trap detritus and injure the fish's delicate belly.

Decor: Provide ample live rock (1.5–2 lbs per gallon) for hiding spots, territorial boundaries, and perching. Clark's Clownfish are semi-aggressive and will claim a specific area of the tank. Include caves, overhangs, and vertical structures. If hosting an anemone is desired, Entacmaea quadricolor (Bubble-tip Anemone) is the most reliable companion, though the fish may also accept Stichodactyla haddoni or Heteractis aurora.

Tank mates: Compatible with other peaceful-to-moderate community fish such as Chromis viridis (Green Chromis), Pterapogon kauderni (Banggai Cardinalfish), Nemateleotris magnifica (Firefish), and Escenius stigmatura (Tailspot Blenny). Avoid aggressive species like Pygoplites diacanthus (Regal Angelfish) or large triggers. Conspecifics: keep only one mated pair or a bonded group; adding a new clownfish to an established pair often results in fatal aggression.

Water Parameters

Parameter	Optimal Range	Notes
Temperature	74–82°F (23–28°C)	Stable at 78°F (25.5°C) is ideal
pH	8.1–8.4	Maintain with aragonite substrate or kalkwasser
Salinity	1.023–1.025 SG (32–35 ppt)	Use a refractometer for accuracy
Alkalinity (dKH)	8–12 dKH	Supports coral growth if present
Ammonia (NH₃)	0 ppm	Highly toxic; must be undetectable
Nitrite (NO₂⁻)	0 ppm	Even trace levels stress fish
Nitrate (NO₃⁻)	< 20 ppm (ideally < 10 ppm)	Clark's tolerates up to 40 ppm short-term, but long-term exposure causes health issues
Phosphate (PO₄³⁻)	< 0.05 ppm	Excess promotes algae and reduces water quality

Key fact: Clark's Clownfish is one of the most euryhaline clownfish species, tolerating brief salinity swings from 1.018 to 1.028, but stable parameters are essential for long-term health.

Filtration and Lighting

Filtration: A sump-based system with a protein skimmer (rated for 1.5–2x tank volume) is strongly recommended. Use a combination of mechanical (filter socks or pads), biological (live rock or ceramic media), and chemical filtration (activated carbon, changed monthly). For smaller tanks (30–40 gallons), a high-quality hang-on-back (HOB) filter rated for the tank size can suffice if paired with frequent water changes. Flow preference: Moderate to strong. Clark's Clownfish naturally inhabit reef zones with surge and current. Aim for a turnover rate of 10–15x tank volume per hour. Use a wavemaker or powerhead to create random, non-linear flow. Dead spots should be minimized.

Lighting: If keeping only fish, standard LED or T5 lighting (8–10 hours per day) is adequate to support a natural day-night cycle. If hosting anemones or corals, upgrade to full-spectrum reef LEDs (e.g., Ecotech Radion, AI Hydra) with a PAR output of 100–200 µmol/m²/s at the anemone's location. The fish itself does not require intense light, but a photoperiod of 8–10 hours helps regulate behavior and reduces stress.

Diet and Nutrition

Staple food: High-quality marine flake or pellet food (e.g., Hikari Marine S, New Life Spectrum Thera+A) as the base diet. Treats: Offer frozen or live foods 3–5 times per week: Artemia (brine shrimp, enriched with Spirulina), Mysis shrimp, chopped krill, and finely minced seafood (shrimp, squid, clam). Clark's Clownfish are omnivorous with a carnivorous lean; in the wild, they consume copepods, amphipods, zooplankton, and algae.

Feeding frequency: Adult fish: 2 small meals per day (morning and evening). Juveniles: 3–4 small meals per day. Portion rule: Feed only what the fish can consume in 2–3 minutes per feeding. Overfeeding is the primary cause of nitrate buildup and obesity in captive clownfish. Uneaten food should be siphoned out immediately.

Supplements

Clark's Clownfish do not require specialized dietary supplements if fed a varied, high-quality diet. However, the following are beneficial in a closed system:

• Vitamin C and E: Add a liquid vitamin supplement (e.g., Selcon, Vita-Chem) to frozen foods 2–3 times per week to boost immune function and color vibrancy.
• Garlic extract: Soak foods in garlic-based additive (e.g., Garlic Guard) to enhance appetite and deter parasites like Cryptocaryon irritans (marine ich).
• Iodine: Not typically needed in the diet, but if the fish hosts an anemone, trace iodine supplementation (as part of a balanced reef additive) supports anemone health, which indirectly benefits the clownfish.
• Calcium and alkalinity: Only relevant if keeping stony corals or anemones; not required for the fish alone.

Common Health Issues

1. Marine Ich (Cryptocaryon irritans) — Symptoms: White salt-like spots on fins and body, flashing (rubbing against objects), rapid breathing, lethargy. Treatment: Quarantine tank with hyposalinity (1.009–1.011 SG for 4–6 weeks) or copper-based medication (e.g., Cupramine). UV sterilizer and formalin baths can help. Avoid copper in a display tank with invertebrates.
2. Brooklynellosis (Clownfish Disease) — Symptoms: Sloughing skin, cloudy eyes, rapid breathing, white or gray patches, lethargy. Often fatal if untreated. Treatment: Freshwater dip (3–5 minutes, pH-matched), followed by formalin baths (1 ml per 10 gallons) or metronidazole in a quarantine tank. Increased water temperature to 80°F (26.7°C) may slow parasite reproduction.
3. Velvet Disease (Amyloodinium ocellatum) — Symptoms: Fine golden or brown dust on skin, clamped fins, flashing, respiratory distress. Treatment: Dim lights (parasite is photosynthetic), copper treatment (same as ich), or chloroquine phosphate. Quarantine essential.
4. Fin Rot (Bacterial) — Symptoms: Frayed, discolored fins with reddened bases, often secondary to poor water quality or injury. Treatment: Improve water parameters (zero ammonia/nitrite, low nitrate), treat with broad-spectrum antibiotics (e.g., Maracyn-Two or Furan-2) in a quarantine tank. Add Indian almond leaves to promote healing.
5. Lymphocystis (Viral) — Symptoms: Cauliflower-like white nodules on fins or body, slow-growing, usually non-lethal. Treatment: No cure; improve water quality and nutrition to boost immunity. Nodules typically resolve in 4–8 weeks. Do not scrape off, as this can cause secondary infection.

Beginner Mistakes

• Adding the fish to an uncycled tank. Clark's Clownfish are hardy but cannot survive ammonia or nitrite spikes. Always cycle the tank fully (ammonia and nitrite at 0 ppm for at least 2 weeks) before introduction.
• Keeping multiple males without a stable hierarchy. In a group, the largest individual becomes the dominant female. Adding several similar-sized fish can lead to constant fighting. Introduce a bonded pair or a single juvenile to avoid aggression.
• Ignoring quarantine for new fish. Even healthy-looking clownfish can carry Cryptocaryon or Amyloodinium without visible symptoms. A 4–6 week quarantine in a separate tank with prophylactic treatment (e.g., hyposalinity or copper) prevents introducing disease to the display tank.
• Overfeeding and under-maintaining water quality. Clark's Clownfish are enthusiastic eaters and will beg for food. Overfeeding leads to high nitrate, phosphate, and obesity. Stick to the 2–3 minute rule and perform weekly 10–20% water changes.

FAQ

Can Clark's Clownfish be kept without an anemone?

Yes. In captivity, they will often host artificial structures such as PVC pipes, flower pots, or large-polyp corals (e.g., Euphyllia). Anemones are not required for their survival, though they may display more natural behaviors if one is provided.

How can I tell if my Clark's Clownfish is male or female?

All clownfish are born male (protandrous hermaphrodites). The dominant individual in a group or pair becomes the female. Females are noticeably larger and more aggressive. Juveniles and subdominant males are smaller and often less boldly colored.

Why is my Clark's Clownfish swimming upside down or twitching?

This behavior often indicates a parasitic infection (e.g., Amyloodinium or Brooklynella) or poor water quality. Immediately test ammonia, nitrite, and nitrate. If parameters are normal, observe for external signs like spots or slime. Quarantine and treat accordingly.

What is the lifespan of Clark's Clownfish in an aquarium?

With proper care, they can live 12–15 years, with some individuals reaching 20 years. Stable water parameters, a varied diet, and low stress are key to longevity.

Can I breed Clark's Clownfish at home?

Yes, they are one of the easier clownfish to breed in captivity. A mated pair will lay eggs on a flat surface (e.g., a terracotta tile or rock) near a strong current. The male guards and fans the eggs. Larvae hatch after 6–8 days and require rotifers, then Artemia nauplii. A dedicated breeding tank with dim lighting and gentle flow is recommended.

References