Coral, sometimes referred to as the “rain-forest of the sea”, are considered one of the more productive ecosystems on Earth. They are also known for their beauty and richness of life. A coral reef is made up of many colonies of coral. Hard coral attach themselves to a reef, often on top of previous coral colonies, thus building their future and providing more stunning color and beauty to the vast ocean.
Image by NOAA’s National Ocean Service
Although there are many different kinds of coral, there are two basic types: hard and soft. Hard coral are known as the reef builders, while soft coral look more like the colorful underwater plants.
Hard coral can be found in a variety of shapes and sizes, however, unlike their soft counterpart, hard coral are usually found in shallow waters where they can be closer to the sunlight.
They are composed of rigid calcium carbonate (limestone) and can sometimes be mistaken for rocks. The Great Coral Reef is an example of when huge colonies of hard coral live and grow together. Here are some examples of hard coral:
Brain coral contain many rough ridges much like the human brain. Their crevices make an ideal place for small animals to live.
Image by jayhem
Image by sethbienek
Star coral kind of look like a decorative custard tart…but they are definitely not for eating. They have an outer ring with lots of lines going through it, then an indentation in the middle.
Image by JennyHuang
Encrusting coral are built extremely strong and can withstand storm conditions. They form by spreading out low, like a crust, on rocky surfaces.
Image by pareeerica
Image by yeowatzup
Pillar coral, like it’s name, look like fingers or pillars sticking upward. They are different from branching coral because they do not have secondary branches. They are commonly found in the western Atlantic Ocean.
Image by Nick Hobgood
Table coral got their name possibly because they have a broad horizontal surface, quite like a standard table. They are normally found in environments with bright light.
Image by BBM Explorer
Image by Hamed Saber
Elkhorn coral is the most common, as well as the largest coral. Its branches, which look like antlers, are thick and very sturdy. Elkhorn coral often acts as a protection for smaller fragile coral and can usually be found on the outer edges of a reef.
Image by Paul and Jill
Image by Paul and Jill
Staghorn coral is a branching coral and like the Elkhorn coral, they also have a lot of antlers. Staghorn coral has a number of main branches, as well as many secondary branches which are used to provide shelter for the rest of a coral reef.
Image by Nick Hobgood
Image by SarahDepper
Bubble coral have large water filled bubbles which cover large sharp sepia. The “bubbles” expand during the day and look very similar to cream colored grapes.
Image by CybersamX
As most of you know, coral reefs form large sections of the Bali coastline. These coral reefs are important for the marine habitat, providing shelter for marine life, protecting the coast against erosion and as a breeding ground for fish. 
