The coral reef is described to be the most complex "habitat" of the oceans.Coral reefs have a number of factors that restrict their location:

• The temperature of the water must be above 18 degrees C;(around 50-70 degrees F.)
• Coral reefs can only grow at a maximum depth of 100 feet (70 meters).
• The water must be clear (not murky) to allow for sufficient light; for example if the coral bed is in a murky bay, the depth is very much restricted. (to much less than 100 feet)
• The water must not only be clear, but also it must be sediment-free; sediment for example mud and sand can clog up the coral polyps.

Coral reefs are formed from a very wide variety of biological life forms. The coral itself is made up of millions of reef building "animals" (related to sea anemones) which secrete massive calcium-like skeletons.One of the reasons for their restriction to shallow and clear water is due to the fact that microscopic plants live within the coral and require the (sun)light for photosynthesis. This provides the coral with oxygen; and the plants receive protection, and elements that the coral secretes for photosynthesis (F.Y.I. This sharing of each others' products is called SYMBIOSIS.)The coral itself is a colony of nocturnal animals that live as polyps. They emerge from their skeleton at night to eat (the small plankton)

The number of species in a certain locale depends upon the ocean; for example, there are more than 700 species of coral in the Indo-Pacific areas, and only 35 species in the Atlantic ocean. The longest, largest and most "vivacious" reefs occur around the Equator; for example the Great Barrier Reef of Australia which runs over 1000 miles from New Guinea to Queensland!(This is also the home of the "Great White Shark"!)

The coral reefs come in one of 3 possible forms:

1. The Fringing reef is a short distance from the shore and is separated from the seashore by Shallow water.
2. The Barrier Reef is a farther distance from the shore, and is separated from the shore by much more sea-water (often one needs to take a boat to this type of reef).
3. The Atoll is a "ring" of coral surrounding a body of water. (Usually the Atoll represents the fringes of a former volcanoe!-[I have to make sure of this])

Entire Books have been written on the subject of the coral reef so I will not do so...:-) Briefly Coral may be hard or soft; may sting or cause trauma due to their sharp calcium carbonate skeletons; some can grow up to 1-2 inches a year (2-5 cm).

The reef may include sponges, sea anemones, starfish (1 in particular [The Crown of Thorns] is causing a lot of harm to the corals making up the Great Barrier Reef), a large variety of fish (some friend, some foe) shellfish (again some are predators, others not), Sea Urchins, Sea Cucumbers (which eat the dead coral skeletons) and so on...