Fish diurnal

Australian Gregory

Plectroglyphidodon apicalis

The feisty gardener of the Australian reef, the Australian Gregory is a bold damselfish that fiercely protects its private algal patches. Small in size but big in personality, this 'farmer' fish is a favorite for underwater observers.

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Quick Identification

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Size

Typically grows to a length of 10-15 cm (4-6 inches).

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Colors

Deep brownish-grey to charcoal body; distinct yellow to orange-yellow tips on the soft part of the dorsal fin and the upper and lower lobes of the tail; scales often have dark margins creating a mesh-like appearance.

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Key Features

Bright yellow or orange highlights on the tips of the dorsal and caudal fins
Dark-edged scales forming a subtle honeycomb pattern
Deep, oval-shaped body with a blunt snout
Aggressive territorial behavior near rocky or coral crevices

When You’ll See Them

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Activity pattern diurnal

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Peak hours 8 AM - 4 PM

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Season Year-round

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Diet Primarily herbivorous; it meticulously farms and eats filamentous algae. It also supplements its diet with small amounts of organic detritus and tiny invertebrates living within its algal mats.

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Habitat Found in shallow coastal reefs, rocky headlands, and sheltered lagoons, usually at depths of 1 to 5 meters.

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Behavior

The Australian Gregory is a small but incredibly feisty member of the damselfish family. It is best known for its role as a "farmer" of the reef. Unlike many fish that wander in search of food, the Gregory claims a specific territory—usually a flat rock or a coral head—and vigorously defends it. Within this territory, it encourages the growth of a specific type of filamentous algae, which it harvests for food. It will even "weed" its garden by removing unwanted species of algae or debris to keep its crop healthy.

Socially, these fish are intensely solitary and highly aggressive toward intruders, regardless of size. They are famous among snorkelers and divers for charging at anyone who gets too close to their patch. This territorial nature makes them easy to observe once you’ve located their home, as they rarely stray more than a meter from their chosen garden. They spend most of their daylight hours patrolling their borders and tidying their algal mats.

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Camera Tips

To capture high-quality footage of an Australian Gregory, you will need an underwater action camera or a specialized marine trail camera. Because these fish are strictly territorial, the secret is to locate their "farm." Look for a specific patch of rock or coral in shallow water that looks slightly furrier or greener than the surrounding area, usually guarded by a single dark fish. Secure your camera to a weighted base or a small tripod and place it on the seabed roughly 30 to 50 centimeters away from the center of the fish's territory.

Placement is everything with this species. Aim for a depth of 1-3 meters where sunlight is strongest. Position the camera at a low angle, looking slightly upward; this helps capture the sunlight hitting the yellow tips of their fins, which are their most distinguishing feature. Because the Gregory is naturally inquisitive and defensive, it will likely approach the camera to investigate or even attack the lens. This boldness allows for incredible close-up shots that would be impossible with more skittish species. Set your camera to a high frame rate (at least 60fps) to catch their rapid, darting movements as they patrol their borders.

For those with "backyard" access to coastal canals, jetties, or rocky shorelines, timing your recording with the high tide is often best, as it brings clearer water and more active feeding behavior. Avoid using bait or lures; the Gregory is an herbivore and is much more interested in protecting its garden than in supplemental food. In fact, the mere presence of the camera is often enough of a stimulus to trigger a series of fascinating territorial displays. Ensure your housing is clean and free of salt spots to make the most of the midday sun, which provides the best natural lighting for underwater videography.

Similar Species

Species that look similar or are commonly confused with Australian Gregory.

Dusky Damsel

The Dusky Damsel has a similar dark body but lacks the bright yellow fin tips and often lives in more crowded colonies.

White-bar Gregory

This relative is identified by a prominent vertical white bar on the middle of its body, which the Australian Gregory never possesses.

Frequently Asked Questions

Yes, they are highly territorial. They will aggressively defend their 'algal gardens' from other fish and even snorkelers who venture too close to their home range.

Look for a dark, brownish-grey damselfish with distinct yellow or orange-yellow tips on its dorsal and tail fins. They are usually found hovering over a specific patch of rock or coral.

They are primarily herbivores. They 'farm' and eat filamentous algae from a specific territory that they keep clean of debris and other competitors.

They are native to the Western Pacific, commonly found along the east coast of Australia, including the Great Barrier Reef, and as far south as New South Wales in shallow, rocky environments.

Yes, because they inhabit very shallow water (often less than 2 meters deep), they are frequently visible to snorkelers or even from the surface near rocky headlands and jetties.

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