FishMarineIntermediate
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Galapagos damselfish
Stegastes beebei
A fiercely territorial damselfish endemic to the Galapagos. Adults are dark grey while juveniles display brilliant neon-blue. It relentlessly farms and guards its turf algae garden from all intruders.
Water Temperature
20 - 27 °C
pH Value
8.1 - 8.4
Water type
Marine
Tank level
Bottom and middle
Adult size
15 cm
Minimum tank volume
>= 300 L
Minimum group
>= 1
KH
8 - 12 dKH
Species description
Geographical Origin and Habitat: Stegastes beebei is a subtropical marine fish endemic to the Eastern Pacific Ocean, specifically distributed around the Galapagos Islands, Cocos Island, and occasionally along the coastlines of Ecuador and Costa Rica. It inhabits exposed rocky coastlines, shallow volcanic reefs, and wave-swept zones at depths of 1 to 20 meters, where strong currents provide a continuous supply of food.
Taxonomy and Morphology: Belonging to the family Pomacentridae, subfamily Pomacentrinae, this species has a robust, oval, and laterally compressed body. It features a blunt head profile and a small mouth lined with a single row of incisiform teeth specialized for scraping algae off rocky substrates. Adults reach an impressive size for a damselfish, up to 13-15 cm in length.
Social Behavior: Typical of the genus Stegastes, this species is highly solitary and aggressively territorial. Each individual establishes and defends a specific territory containing a 'turf algae garden,' which it cultivates and guards against any intruders, including much larger fish and even human divers. They do not tolerate other members of their species or similar-looking fish.
Coloration and Sexual Dimorphism: Adult coloration is uniform charcoal grey, dark brown, or black, sometimes with a subtle bluish sheen on the margins of the scales. In contrast, juveniles are spectacularly colored, featuring a bright neon-blue body with a black spot ringed in electric blue on the dorsal fin and a blue stripe on the head. No external sexual dimorphism is present between mature males and females.
Care, breeding and tankmates
Aquarium Setup: A minimum aquarium volume of 250 liters is required for a single specimen due to its intense aggression and territorial requirements. The aquascape should feature a large amount of live rock arranged to create natural caves, crevices, and visual barriers, allowing the fish to claim a defined territory and feel secure.
Diet and Feeding: Omnivorous with a strong herbivorous tendency. In the wild, they consume filamentous algae and small invertebrates associated with their algae turfs. In captivity, feed them high-quality spirulina flakes, herbivore pellets, nori seaweed, and fresh blanched vegetables like zucchini, supplemented with frozen foods such as mysis, krill, and brine shrimp.
Water Quality: Because it comes from subtropical waters, it thrives at slightly cooler temperatures than typical tropical reef fish, with an ideal range of 20 to 25 °C. Keep pH stable between 8.1 and 8.4, and specific gravity between 1.021 and 1.025. Strong water movement and efficient filtration are necessary to keep the water well-oxygenated.
Compatibility and Cohabitation: Highly aggressive and difficult to keep in a standard community tank. It will harass peaceful, slow-moving, or smaller tankmates. It should only be housed with large, robust, and fast-moving fish such as large surgeonfish, triggerfish, or large wrasses. Do not house with other damselfishes or similar oval-bodied species.
Aquarium Breeding: Breeding in home aquariums is rare due to their aggressive nature, which makes pair bonding difficult. They are oviparous broadcast-spawners. During spawning, the male prepares a nesting site on a flat rock surface and courts the female. After fertilization, the male alone guards and fans the adhesive eggs until they hatch.
Risks and Diseases: An exceptionally hardy fish with strong resistance to most common marine parasites like ich. The main risks are physical injuries resulting from territorial fights if the aquarium is too small or lacks sufficient structural dividers. It is a very resilient species, making it suitable for hobbyists who can manage its temperament.
Geographic Origin and Distribution
Stegastes beebei is a subtropical marine fish endemic to the Eastern Pacific Ocean, specifically distributed around the Galapagos Islands, Cocos Island, and occasionally along the coastlines of Ecuador and Costa Rica. It inhabits exposed rocky coastlines, shallow volcanic reefs, and wave-swept zones at depths of 1 to 20 meters, where strong currents provide a continuous supply of food.
Origin
Tropical oceans and reefsExtra-Amazon South AmericaCentral America and Caribbean
Fish profile
- Temperament
- Aggressive
- Behaviorally, the Galapagos Ringtail Damselfish is characterized as being highly territorial. They exhibit fascinating social dynamics that can be a true joy to observe in a well-planned display. While generally agreeable, unexpected aggression can sometimes occur if their fundamental environmental needs are not met. Providing adequate hiding spots and sufficient swimming space will go a long way in ensuring their temperament remains calm and manageable.
- Diet
- Omnivore
- This species is known to be a herbivorous in its natural habitat, requiring a varied diet in captivity. To ensure optimal health and coloration, provide high-quality prepared foods alongside live or frozen options like brine shrimp or bloodworms. It is essential to match the food particle size to the fish's mouth structure to facilitate easy consumption. Regular rotation of dietary items will prevent nutritional deficiencies and keep the fish highly active.
- Life expectancy
- 27 years
- In the wild, this species displays an extraordinary longevity for a fish of this size, with a lifespan that can reach up to 27 years. This remarkable durability is linked to its sedentary lifestyle and the protection offered by its territory. In captivity, its lifespan depends on the stability of the saltwater and the absence of competitive stress.
- Adult size
- 15 cm
- The catalog's scalar value is 15 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 15 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Stegastes beebei (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Solitary
- Maintaining an appropriate sex ratio is vital, and a balanced distribution of males and females often works best for the Galapagos Ringtail Damselfish. In many cases, keeping a ratio heavily skewed towards females can help disperse male aggression during the breeding season. It is important to monitor the group dynamics closely to quickly identify and isolate any bullied individuals. A well-structured environment with plenty of visual barriers will support a harmonious mixed-sex group.
- Feeding frequency
- Twice daily
- Establishing a consistent feeding routine is important, with 1-2 small meals per day being ideal for the Galapagos Ringtail Damselfish. Aquarists should carefully monitor the fish during feeding time to ensure every individual gets its share. Any uneaten food should be promptly removed with a net or siphon to preserve the pristine aquatic environment. During periods of breeding or elevated temperatures, the feeding frequency may be slightly increased.
- Bioload
- The Galapagos Ringtail Damselfish (Stegastes beebei) produces a moderate bioload in the home aquarium. Proper filtration is an absolute necessity to handle the waste output generated by this species. Enthusiasts should be prepared to maintain a strict water change regimen to keep parameters stable. Monitoring the biological capacity of the tank will ultimately prevent unwanted algae spikes and water quality deterioration.
- Flow
- Strong
- Providing a moderate to strong current is highly recommended for the overall well-being of the Galapagos Ringtail Damselfish. Adequate water circulation not only mimics their natural ecosystem but also ensures high dissolved oxygen levels throughout the aquarium. Hobbyists should avoid creating localized dead spots where debris might accumulate. Adjusting the filtration output angle can help achieve the perfect balance between steady circulation and calm resting areas.
- Jump risk
- No
- Reproduction
- Oviparous
- As a known benthic egg layer, the Galapagos Ringtail Damselfish exhibits fascinating breeding behaviors when conditions are optimal. Providing a separate, specialized breeding setup is often the best approach to ensure a high yield of fry. Parents may require removal post-spawning depending on the specific parental care traits of the species. Raising the young demands pristine water parameters and a steady supply of infusoria or newly hatched artemia.
- Compatibility & tankmates
- Reef safe
- The Galapagos Ringtail Damselfish is known to be aggressive towards other damsels and timid fish when integrated into a carefully planned setup. They tend to exhibit the best colors and natural behaviors when kept with species of a similar temperament. Aquarists must be cautious to provide enough visual barriers if housing them with semi-aggressive tankmates. Overall, a well-thought-out stocking plan will yield a beautiful, drama-free aquatic display.
- Tank level
- Middle/Bottom
- This species is predominantly a all levels dweller within the aquarium setup. Providing the appropriate spatial layout with open swimming areas or dense vegetation where they feel secure is highly beneficial. By understanding their preferred depth, aquarists can carefully select complementary species that occupy other regions of the tank. This spatial separation helps to reduce competition for food and minimizes unnecessary territorial disputes.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3 ± 0.44 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.02089, b = 2.98
- VulnerabilityLow vulnerability (23 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
