Coral Reef

Ocean Article

Although coral reef are often mistaken for rocks or plants, they are actually composed of tiny, fragile animals called polyps. A polyp is a spineless animal. Polyps can be the size of a pinhead while others are larger, sometimes a foot in diameter. One coral branch is covered by thousands of these animals.

A polyp has a sac-like body and an opening or mouth encircled by stinging tentacles called cnidae. The polyp uses calcium carbonate from seawater to build itself a hard, cup-shaped skeleton. This limestone skeleton protects the soft, delicate body of the polyp. Polyps are usually nocturnal, meaning that they stay inside their skeletons during the day. At night, polyps extend their tentacles out to feed.

They are generally classified as either "hard coral reef" or "soft coral reef".

Hard Corals

Hard corals reef grow in colonies. Their skeletons are made out of calcium carbonate (also known as limestone) which is hard and eventually becomes rock. Proper lighting is critical, since many corals contain algae in their tissues.

These algae, known as zooxanthellae, have a symbiotic relationship with the coral. It is believe that the algae benefit by being protected in the coral tissue and by receiving a supply of nutrients from the coral.

The coral benefits by using as food some biochemical products of the photosynthetic activities of the algae. True corals should no be attempted by the beginning aquarist.

Soft Corals

Soft corals reef such as sea fingers and sea whips are soft and bendable and often resemble plants or trees. These do not have stony skeletons, but instead grow wood-like cores for support and fleshy rinds for protection. They are referred to as ahermatypes or non-reef building corals and they do not always have zooxanthellae. They are found in both tropical seas and in cool, dark regions.

Maintaining corals in an aquarium is somewhat of a challenge to the new aquarist. Corals are very sensitive to water conditions and most have high dissolve oxygen concentrations, low nitrate, ample supplies of essential trace elements like strontium, and increased water movement. They also required a good supply of calcium for proper growth and ample illumination with the correct intensity and spectrum of light.

Source: Copyright 2002 The Coral Reef Alliance. All rights reserved. The Saltwater Aquarium Handbook. Author: George Blasiola. Copyright 2000, 1991 by Barron’s Educational Series, Inc. All rights reserved.

Marine Related Articles:

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Tomato Clownfish. Coming from the Pacific Ocean this species can become very aggressive with age, however if you can buy a match pair, at the same time, they will often live together in harmony. It can be an excellent choice for the beginner since is very hardy and can live without an anemone.

Maroon Clownfish. Do not move the Maroon Clownfish with a net as its cheekspines will become entangled. Use a specimen container if capture is necessary.

Clarkii Clownfish. The Clarkii Clownfish is one of the most hardy, and therefore, one of the most common clownfish in home aquariums. A 30 gallon or larger aquarium containing an anemone of any type is desirable. It is semi-aggressive towards other clownfish and passive tank mates.

True Percula Clownfish. It can be found individually, or more commonly, in pairs or small groups within the same anemone such as Heteractis magnifica or Stichodactyla mertensii.