What the Arc-Eye Hawkfish Is and Where It Lives

The arc-eye hawkfish is a small, aggressive predator found in Indo-Pacific coral reefs, particularly around the Philippines, Indonesia, and the Great Barrier Reef. It grows to about 4 inches long and gets its name from the curved blue or turquoise line that runs above each eye. The fish has a stocky body, usually tan or reddish with darker bands, and spends most of its time perched on coral heads or rocky outcrops, watching for small fish and crustaceans to hunt.

In the wild, arc-eyes live in shallow reef environments where they can dart quickly between cover. They are solitary hunters and highly territorial—a single fish will claim a small area of reef and defend it aggressively against other arc-eyes and similar-sized fish. This behavior carries over into the aquarium, which is the most important thing to understand before bringing one home.

Key Takeaways

  • Arc-eye hawkfish are aggressive toward other fish their size or smaller and will hunt small fish and shrimp in a tank, so they need careful tank mate selection.
  • They require a minimum 30-gallon tank with plenty of live rock, caves, and perches where they can rest and hunt from cover.
  • Arc-eyes eat small fish, shrimp, and crustaceans in the wild and need a varied diet of frozen and live foods in captivity.
  • They are hardy fish that tolerate a range of water conditions but do best in stable saltwater tanks with good filtration and regular water changes.
  • Hawkfish can live 5 to 7 years in captivity with proper care, making them a long-term commitment.

Tank Size and Setup Requirements

Arc-eye hawkfish need a minimum tank size of 30 gallons, though 40 gallons or larger is better if you plan to keep them with other fish. The tank must have plenty of live rock arranged to create caves, crevices, and elevated perches. Hawkfish are ambush predators and spend much of their time resting on or near rock structures, watching for prey. Without adequate rock work, they become stressed and may hide constantly or behave erratically.

Arrange the rock so there are multiple levels and hiding spots. Hawkfish like to perch on top of rocks or in caves where they have a clear view of the surrounding area. Leave open sand or rubble space in front of these perches so the fish can see approaching prey. The tank should have moderate water flow—not so strong that it pushes the fish around, but enough to keep the water oxygenated and carry food particles through the tank.

Use a reliable heater to maintain water temperature between 72 and 78 degrees Fahrenheit. A protein skimmer and regular water changes (25 percent every two weeks) help keep the tank clean, since hawkfish produce waste and leftover food can foul the water quickly. Lighting is not critical for the fish itself, but if you keep live corals or macroalgae, provide 8 to 10 hours of light per day.

Feeding and Diet

In the wild, arc-eye hawkfish hunt small fish, shrimp, copepods, and other small crustaceans. In captivity, they need a varied diet to stay healthy. Offer frozen foods like mysis shrimp, brine shrimp, and small pieces of fish several times a day. Many arc-eyes also accept small live foods such as ghost shrimp or live brine shrimp, which trigger their hunting instinct and provide enrichment.

Feed juveniles three to four times daily in small amounts. Adult hawkfish can be fed once or twice daily, depending on tank size and whether other fish are present. Watch the fish during feeding to make sure it is eating its share—hawkfish are aggressive feeders and will chase other fish away from food, but in a crowded tank they may not get enough if they are competing with faster swimmers.

Avoid keeping arc-eyes with very small fish or ornamental shrimp, because the hawkfish will hunt them as food. Even fish that seem too large to eat may be attacked if the hawkfish is hungry or territorial. Some keepers report success with larger, faster fish like tangs or jacks, but there is always a risk.

Temperament and Tank Mates

Arc-eye hawkfish are not community fish. They are aggressive toward other hawkfish and will fight to the death if two are placed in the same tank. They also chase and harass smaller fish, and many keepers report that arc-eyes will eventually kill any fish small enough to fit in their mouth, even if the fish seemed safe for weeks.

Larger, fast-moving fish like yellow tangs, blue tangs, or jacks may coexist with an arc-eye, but aggression is not may provide to stay low. Some arc-eyes are more aggressive than others, and stress or hunger can trigger attacks at any time. Peaceful fish like gobies, blennies, and small wrasses are poor choices. Avoid keeping arc-eyes with ornamental shrimp or any crustacean, as they will be hunted.

The safest approach is to keep an arc-eye in a species-only tank or with only large, robust fish that can defend themselves. If you want a community tank, an arc-eye is not the right choice. Many experienced reef keepers keep arc-eyes alone and find them rewarding to observe—they are active, intelligent, and have distinct personalities.

Water Conditions and Maintenance

Arc-eye hawkfish are hardy and tolerate a range of saltwater conditions. They do best in stable tanks where temperature, salinity, and pH do not fluctuate. Maintain salinity between 1.020 and 1.025 (specific gravity), pH between 8.1 and 8.3, and temperature between 72 and 78 degrees Fahrenheit. Use a reliable aquarium thermometer and check it daily, especially if your room temperature changes with the seasons.

Perform a 25 percent water change every two weeks to remove waste and replenish trace elements. If you notice algae blooms, cloudy water, or a foul smell, increase water changes to 25 percent weekly until the tank clears. Test water parameters (ammonia, nitrite, nitrate) monthly using a test kit or by sending a sample to a local aquarium shop. Ammonia and nitrite should always be zero; nitrate should stay below 20 parts per million.

Clean the protein skimmer cup weekly and replace filter media as needed. Live rock will develop beneficial bacteria over time, so avoid replacing all the rock at once. If you need to remove rock for cleaning, do it gradually and rinse it in tank water, not tap water, to preserve the bacteria.

Health Issues and Lifespan

Arc-eye hawkfish are generally hardy and resistant to disease when kept in stable conditions. The most common problems are stress-related, caused by inadequate rock work, poor water quality, or aggression from tank mates. A stressed hawkfish may stop eating, hide constantly, or develop white spots (a sign of ich, a parasitic infection).

If you notice white spots, raise the tank temperature to 78 to 80 degrees Fahrenheit and increase aeration. Some keepers move the fish to a separate treatment tank with copper-based medication, but this should only be done if the spots do not clear within a few days. Prevent ich by maintaining stable water conditions and avoiding sudden temperature changes.

Arc-eye hawkfish live 5 to 7 years in captivity with proper care. Some individuals have been reported to live longer in well-maintained tanks. The key to longevity is consistent feeding, stable water conditions, and minimal stress. A hawkfish that is eating well, active, and perching regularly is likely to live a long, healthy life.

Frequently Asked Questions

Can I keep two arc-eye hawkfish together?

No. Arc-eyes are extremely territorial and will fight aggressively if placed in the same tank. Even a large tank will not prevent conflict. Keep only one arc-eye per tank unless you have extensive experience and can monitor them constantly.

Will an arc-eye eat my corals?

Arc-eyes do not eat corals, but they may damage them by moving rocks or disturbing the substrate while hunting. If you keep corals, place them securely and monitor the hawkfish to make sure it is not knocking them loose.

How often should I feed my arc-eye?

Feed juveniles three to four times daily in small amounts. Adults can be fed once or twice daily. Adjust portions based on how much the fish eats in a few minutes—uneaten food fouls the tank quickly.

What size tank do I need for an arc-eye hawkfish?

A minimum 30-gallon tank is required, though 40 gallons or larger is better if you plan to keep other fish. The tank must have plenty of live rock and hiding spots. A smaller tank will stress the fish and lead to aggression or illness.

Do arc-eye hawkfish need a specific type of food?

Arc-eyes eat small fish, shrimp, and crustaceans in the wild. In captivity, offer frozen mysis shrimp, brine shrimp, and small fish pieces. Live foods like ghost shrimp or live brine shrimp provide enrichment and trigger natural hunting behavior.