Description
Pearl Bubble Hard Coral (Plerogyra sp.)
(Also known as Bubble Coral, Grape Coral, or Pearl Coral)
Overview
The Pearl Bubble Hard Coral (Plerogyra sp.) is a beautiful and distinctive large-polyp stony (LPS) coral, prized for its translucent, pearl-like vesicles that resemble clusters of bubbles or grapes. These bubble-like polyps gently expand and contract throughout the day, giving the coral a soft, fluid appearance. Available in shades of white, green, silver, and cream, the Pearl Bubble Coral adds both texture and elegance to reef aquariums. Hardy, slow-growing, and captivating, it is best suited as a feature coral in low to moderate flow environments.
Origin
Native to the Indo-Pacific region, including the Coral Sea, Great Barrier Reef, Fiji, Tonga, Indonesia, and the Red Sea. Commonly found in shallow, sheltered reef slopes and lagoons, where light is moderate and water movement gentle.
Feeding
The Pearl Bubble Coral is photosynthetic, deriving most of its nutrition from zooxanthellae within its tissues. It also benefits from supplemental feedings that encourage growth and polyp expansion. Feed 1–2 times per week with:
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Mysis or brine shrimp
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Finely chopped seafood
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Marine plankton or LPS coral foods
Target feeding at night or when tentacles are extended will yield the best results.
Lighting
Low to moderate lighting. The bubble-like vesicles are sensitive to intense illumination. Provide diffused light from LED, T5, or hybrid systems.
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PAR range: 75–150 µmol/m²/s
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Avoid direct, high-intensity light that can cause bleaching or tissue retraction.
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Under blue-spectrum lighting, the vesicles exhibit a pearlescent, fluorescent glow.
Water Flow
Low to moderate, indirect flow. Gentle, variable currents are ideal to keep the coral’s bubbles gently swaying while preventing debris from settling. Avoid strong or direct jets of flow, which can tear delicate tissue or cause the vesicles to deflate.
Placement
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Position on the substrate or lower rockwork in a sheltered area with indirect light and flow.
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Provide at least 15 cm (6 inches) of space from other corals to prevent stinging contact.
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Avoid sharp rock edges — the delicate bubbles can rupture easily.
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When fully expanded, colonies can double or triple in apparent size.
Tank Mates
Reef safe with caution. Compatible with:
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Peaceful reef-safe fish (gobies, blennies, clownfish, tangs, etc.)
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Snails, shrimp, and small hermit crabs
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Other non-aggressive LPS or soft corals with sufficient spacing
Avoid:
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Aggressive corals (e.g., Euphyllia, Galaxea, Hydnophora)
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Large angelfish, butterflyfish, or puffers that may nip at the polyps
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Crabs or shrimp that may climb and irritate the bubbles
Aggression
Moderately aggressive. Plerogyra corals extend long, stinging sweeper tentacles at night to defend their territory. Maintain clear spacing from nearby colonies and ensure steady water movement to disperse toxins.
Experience Level
Intermediate. The Pearl Bubble Coral is hardy once established but sensitive to excessive light or flow. Stable water parameters and careful placement are key to long-term success.
Water Parameters
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Temperature: 24–27°C (75–81°F)
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pH: 8.1–8.4
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Salinity: 1.024–1.026 SG
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Alkalinity: 8–12 dKH
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Calcium: 400–450 ppm
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Magnesium: 1250–1350 ppm
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Nitrate: <10 ppm
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Phosphate: <0.03 ppm
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Tank Size: Minimum 100 litres (25 gallons) for a single colony; larger systems preferred for stability
Reef Compatibility
Reef safe with caution. The Pearl Bubble Coral adds dramatic form and movement to mixed reef aquariums, but requires adequate space and gentle flow. Its large, soft vesicles are highly photosensitive and can be damaged by rough handling or high flow, so it’s best displayed in a protected, open area where it can fully expand.
Interesting Fact
Each “bubble” on Plerogyra corals functions as a light-modulating structure — expanding during the day to maximise photosynthesis and deflating slightly at night when feeding tentacles extend to capture plankton from the water column.
