Corals are special living animals. Many people think corals are just rocks, but they are ALIVE and are like humans. They have the same basic need for air, food, sun, and water. There are two different types of corals, soft and stony. The stony corals that build reefs require very specific living conditions. They can grow best in saltwater that is 68-86 degrees Fahrenheit (20-30 degrees Centigrade), clear, shallow and constantly moving. Corals come in amazing shapes - from massive heads to branching thickets. They also grow to different sizes. Some are barely one inch (2.5 centimeters) across, while others reach more than 20 feet in length (6 meters). A very important algae is the zooxanthellae that lives within the coral. Zooxanthellae gives coral color and keeps it healthy. Without it, corals would not be able to survive. Corals belong to a family that consists of jellyfish and sea anemones. Corals reproduce in two ways and there are about 150 different kinds of corals that are still increasing due to cross breeding. The parts of a coral consist of living polyps attached to many millions of dead polyp skeletons. Corals eat by paralyzing or killing their prey with their stinging tentacles.
In Hawai'i there are four common types of stony corals: the lobe, cauliflower, finger, and rice corals. These corals are protected by law, and therefore we should all care for them.