Physogyra

Physogyra, the pearl bubble coral, is closely related to Plerogyra but features smaller, more numerous pearl-like vesicles. During the day, these bubbles inflate for photosynthesis, creating an attractive pearlescent appearance. At night, the bubbles retract to reveal sweeper tentacles. Place them in a sheltered position in the lower to mid tank under moderate PAR (75–150 PAR) with very gentle flow. Like Plerogyra, the delicate bubbles can be damaged by strong current.

Keep water parameters stable: alkalinity 7.5–9.0 dKH, calcium 400–450 ppm, magnesium 1300–1400 ppm, and temperature 25–26 °C. Physogyra benefit from weekly target feeding with small meaty foods when the feeding tentacles emerge at night. They are primarily photosynthetic during the day, with the inflated vesicles maximising light capture. Avoid touching or disturbing the bubbles during daytime maintenance.

Physogyra extend sweeper tentacles at night that can sting neighbouring corals, so provide generous clearance. They prefer sheltered, cave-like positions that replicate their natural habitat on shaded reef walls. Fragging is possible but requires allowing the bubbles to deflate first and cutting carefully to avoid tissue damage. These corals are periodically available from Australian coral retailers and make fascinating additions to tanks with appropriate low-flow refuges.