The sun coral, a captivating marine invertebrate, draws attention with its stunning appearance in aquariums worldwide. Belonging to the genus Tubastraea, these corals are recognized for their distinct, vibrant yellow and orange polyps that resemble small, blooming suns when extended. Their visually striking coloration makes them a popular choice for reef tank enthusiasts.
Natural Habitat and Appearance
Sun corals are classified as large polyp stony (LPS) corals, forming colonies of individual polyps. Each polyp features a central mouth surrounded by tentacles. These corals are azooxanthellate, meaning they do not host symbiotic algae called zooxanthellae. Unlike most corals that rely on sunlight for energy through photosynthesis, sun corals are non-photosynthetic (NPS) and obtain all their nutrition from captured food.
This non-photosynthetic nature dictates their preferred natural habitats. Sun corals are found in the Indo-Pacific region, inhabiting shaded areas of coral reefs such as the undersides of ledges, crevices, and cave ceilings where light penetration is minimal. They also thrive in deeper waters, sometimes exceeding 200 feet (61 meters), and on artificial structures like shipwrecks, where light is similarly scarce.
Aquarium Care and Feeding
Sun corals require direct and frequent feeding. They must be offered meaty foods, as they derive all their energy from what they consume. Suitable food items include frozen mysis shrimp, brine shrimp, krill, chopped seafood, cyclop-eeze, or Artemia nauplii.
“Target feeding” is the most effective method, using a pipette, turkey baster, or syringe to deliver food directly to each polyp. This ensures every polyp receives adequate nutrition, as they may not get enough from general tank feedings. While some hobbyists feed a few times a week, many aquarists find that feeding sun corals several times per day yields the best results, especially during acclimation. It is advised to avoid leaving more than a couple of days between feedings.
Sun corals prefer low-light conditions, mirroring their natural deep or shaded habitats. Placing them in caves or under overhangs in the aquarium simulates this environment and helps prevent undesirable algae growth on their skeletons. Moderate to high water flow is also beneficial, as it aids in delivering food particles to the polyps, which extend their tentacles to capture prey.
The Invasive Sun Coral
While admired in aquariums, certain Tubastraea species, particularly Tubastraea coccinea, are recognized as invasive outside their native Indo-Pacific range. This coral has established populations in the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico. Its introduction is attributed to human activities, with primary vectors being biofouling on ship hulls and attachment to offshore oil and gas platforms. These artificial structures act as stepping stones, facilitating the coral’s spread across vast distances.
The establishment of Tubastraea coccinea in non-native regions poses ecological problems. It exhibits rapid growth, early maturity, and a high reproductive rate, allowing it to quickly colonize available surfaces. This aggressive colonization enables it to outcompete native coral species and other benthic invertebrates for space and resources, potentially altering the structure of native communities. The absence of natural predators in the invaded Atlantic regions contributes to its unchecked proliferation, leading to a reduction in local biodiversity and impacting ecosystem functions.