The Sun Coral, belonging to the genus Tubastraea, is a visually striking organism widely sought after by marine aquarium enthusiasts for its brilliant yellow or orange coloration and large, flower-like polyps. This species is often displayed in reef tanks, providing a splash of color that is active when many other corals are closed. However, the coral’s popularity in the trade stands in sharp contrast to its global reputation as an aggressively invasive species outside of its native Indo-Pacific range. The conflict between the Sun Coral’s aesthetic appeal and its ecological threat highlights the complex responsibilities involved in maintaining non-native marine life.
Unique Biological Characteristics
The Sun Coral is defined by its azooxanthellate status, meaning it lacks the symbiotic algae, zooxanthellae, that provide most reef corals with energy through photosynthesis. This dictates that Tubastraea species do not rely on light for sustenance and can even thrive in dark environments. In nature, these corals are often found in shaded areas such as caves, overhangs, and beneath docks, where light penetration is minimal.
Sun Corals are obligate heterotrophs, capturing plankton and other meaty particles directly from the water column with their tentacles. Their polyps are typically extended at night when zooplankton is most abundant, although they can be “trained” to open during the day through consistent, targeted feeding. This reliance on external food sources contributes to their rapid growth rate. The ability to thrive in low-light, food-rich environments with low substrate selectivity is a major factor in their success as an invasive organism.
Specific Requirements for Aquarium Maintenance
Caring for Sun Corals successfully revolves around consistent, targeted feeding. Since they do not absorb light for energy, they must be given small, meaty foods directly to each polyp multiple times per week, with daily feeding often recommended for optimal health and growth. Suitable foods include enriched brine shrimp, mysis shrimp, and finely chopped seafood.
Hobbyists should use a pipette or turkey baster to deliver food directly onto the extended polyps, often after turning off the aquarium’s pumps to prevent the food from being washed away. This heavy feeding regimen introduces a significant amount of nutrients into the aquarium, meaning that robust filtration and aggressive water change schedules are necessary to prevent undesirable algae growth. While Sun Corals do not require intense lighting, they do benefit from moderate to strong water flow, which helps carry food particles to the colony and prevents detritus from settling.
Sun Corals build a stony skeleton, requiring the maintenance of standard marine water parameters, including salinity, temperature, alkalinity, and calcium. Unlike photosynthetic corals, Tubastraea species can tolerate slightly elevated nitrate and phosphate levels due to the heavy feeding they require. Placement in the tank should prioritize accessibility for feeding, even if that means placing them in a well-lit area, as the presence of light does not harm them.
Global Ecological Impact
In the wild, the genus Tubastraea has become a marine invader, primarily due to its hardy nature and efficient reproductive strategies. Originating from the Indo-Pacific, species like T. coccinea have established dense populations in non-native areas, notably the Western Atlantic, including the Gulf of Mexico, the Caribbean, and along the coast of Brazil. The primary mechanism for this long-distance spread is fouling on artificial structures, such as the hulls of ships and oil and gas platforms.
These corals thrive on these artificial substrates. Once established, Sun Corals outcompete native, slow-growing corals for space by rapidly colonizing available surfaces. Their aggressive growth and ability to settle on diverse substrates, including metal, plastic, and rock, allow them to dominate habitats that native species cannot.
The reproductive strategy of Tubastraea aids its invasive success, as it can reproduce continuously throughout the year and releases larvae that settle quickly after a short period in the water column. These characteristics, combined with the species’ ability to tolerate conditions that cause native zooxanthellate corals to bleach and die, make it resilient. The presence of these invasive corals has prompted control and eradication programs in regions like Brazil to protect vulnerable native reef communities.
Responsible Management in the Home Aquarium
Responsible management by hobbyists is a matter of environmental protection. The most important rule is the prohibition of releasing any live coral material or aquarium water into local waterways or storm drains. Even small fragments or water containing released larvae pose a risk of establishing new populations in coastal environments.
Within the home aquarium, hobbyists can contain the coral’s growth to prevent it from spreading. Placing the colony on a small, isolated rock island or within the sump can control its physical spread through fragmentation or basal growth. If trimming is required, all removed fragments must be fully dried out or chemically treated with household bleach before disposal. Ensuring that any new Tubastraea purchased is captive-propagated or ethically sourced from non-invasive regions also helps reduce the demand for wild-collected specimens.