What are corals - Hard coral habitat - 1366x666

What are corals?


What are corals - Coral 2 What are corals - Coral 1 

They have been described in many ways: boulders, plants, upside-down sea jellies, unidentified inanimate objects in the ocean. Thanks to their branching structures and rock-like appearances, it’s no surprise they are often mistaken as marine plants or boulders. Corals are in fact living organisms - they are animals instead of plants! Corals, unlike plants, do not produce their own food through photosynthesis. They obtain food and other nutrients from external sources.

When you observe an entire coral structure, you are actually looking at thousands of coral organisms. A single coral organism exists as a polyp. These coral polyps are extremely small and soft-bodied, each with a mouth surrounded by stinging tentacles . 

Corals have two ways of obtaining nutrients. First is with the help of a symbiotic algae, known as zooxanthellae, which live within coral tissues. The algae carry out photosynthesis in which they absorb sunlight and produce food for themselves and the corals that house them. The second way of obtaining nutrients is through the use of their stinging tentacles to capture and pull free-floating plankton to their mouths.

S.E.A. Aquarium – Home to one of the world’s largest live coral displays


Did you know S.E.A. Aquarium has one of the largest live coral displays in the world? We have over 100 species of hard coral and at least 20 species of soft corals that can be found across 13 habitats. Our largest collection of hard corals are grown in a 28,000-litre habitat! Hard corals are reef-building corals and have hard skeletons made up of calcium carbonate, while soft corals do not.

The facilities in S.E.A. Aquarium provide a safe haven for rescued corals. In 2017, 80 pieces of illegally-imported corals from the Philippines were seized by the authorities and placed under our care. Most of them were in poor condition, having rotting structures or insufficient energy to feed properly. Our dedicated curatorial and animal health teams closely monitored and nursed these corals to good health. 

Through the showcase of vibrant and beautiful coral displays, we hope to generate greater interest and awareness on their fascinating way of life, the teeming life that corals support, as well as their importance to our ecosystem. The controlled environment in aquariums facilitates more robust research that might be challenging to conduct in wild populations. Observations and research on corals can deepen our understanding on their nutrition, responses to varied environmental conditions, and propagation mechanisms, which in turn contributes to improved coral husbandry and potential restoration or conservation efforts.


Maintaining coral habitats in S.E.A. Aquarium



Not all coral species co-exist well. When placing different species together in a habitat, aquarists need to ensure they do not block or sting others.

Maintenance also requires careful clearance of sedimentation. Suspended particles can turn the water murky and reduce the amount of light available for the zooxanthellae living inside corals to photosynthesise. Heavy sedimentation can smother corals. In the ocean, the waves clear out sedimentation and wastes from corals. In our habitats, a wave pump is installed to simulate wave actions for sedimentation clearance.

Most of the corals in S.E.A. Aquarium are photosynthetic, so lighting is a very important energy source. This is why bulbs have to be changed occasionally even when they are working fine to ensure the light intensity is always kept at a constant and optimal threshold.

To supplement the corals’ diet, planktonic food is also provided. Aquarists often conduct broadcast feeding in the coral habitats where the planktonic food are distributed using a turkey baster. 

Lastly, most coral species are sensitive to water temperature and even pH changes. Routine water quality tests have to be carried out to ensure the water parameters are constantly met.



What are corals - Coral fragments What are corals - propagation tank 

Corals reproduce sexually and asexually. Sexual reproduction involves the production of eggs and sperms. Corals undergo spawning - a process where eggs and sperms are released and external fertilisation takes place in the water. Coral species will spawn simultaneously in mass spawning events. These events occur only once a year and usually last a few nights after the occurrence of a full moon during a specific period that differs across regions. In Singapore, mass spawning can usually be observed in late March or April. 

Asexual reproduction involves budding or fragmentation. This does not involve any fertilisation as new polyps bud off from the parent polyp, reattach to a substrate, and grow into a separate colony. This makes the new colony an exact genetic clone of the original. This budding ability is what our aquarists utilise when propagating corals.

In S.E.A. Aquarium, corals are cultured by a process called “fragging”. A coral fragment is broken off from a colony and taken to the fragging tank for it to grow. It grows based on the principle of budding whereby the newly-formed colony is a clone of the parent colony. These coral fragments are grown in two open top tanks found at back-of-house areas, and are set up with equipment that provides the optimum light, water flow, and parameters. 

Once the corals reach a significant size, the aquarists will carefully place them back in the habitats. In-house culturing of corals allows S.E.A. Aquarium to be self-sustainable in the acquisition of corals as it reduces the need to harvest these animals from the ocean. It also gives aquarists first-hand experience on understanding the needs of corals and learn about the different environmental requirements of each species.


Why should we protect corals and coral reefs?

Coral reefs are spectacular ecosystems and they play home for 25% of the world’s marine life. They support various marine life by providing shelter, food, breeding and nursery grounds for these organisms. Furthermore, most of the fishes that reside in coral reefs are a crucial source of seafood for humans, providing sustenance and livelihood. Additionally, they act as barriers that protect shorelines from erosions, storms, and tsunamis. Given their heightened sensitivity to environmental conditions, diverse coral communities are being especially threatened by rapid changes that include elevated sea temperatures, increased acidity, destructive fishing, and pollution. Over the past 30 years, more than half of the world’s coral reefs have perished, and up to 90% may die over the next 20 years. 

Our dedicated aquarists continue to work hard behind the scenes, ensuring the best care for our corals and propagating them sustainably, in the hope that we can contribute to the recovery of wild populations in the near future.

You can be a part of S.E.A. Aquarium’s coral conservation efforts by doing the following: 

  • Counter global warming – turn off electrical appliances whenever possible to reduce your energy consumption.
  • Consume seafood products from brands that have sustainability certifications and do not use destructive fishing methods. 
  • Dispose your litter responsibly so that it does not end up in the ocean.
  • Do not purchase products or souvenirs that contain coral.
  • Support operators and businesses in tourism that are eco-friendly and champion marine conservation. 


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