Coral as a kind of creature in the ocean, because of its beautiful appearance and loved by people, coral has various colors.

Its color is related to its symbiotic algae, for example: worm yellow algae.

When the number of symbiotic algae in the coral decreases, it will cause the phenomenon of coral bleaching.

So, the color of coral bone itself is often white, but also a small amount of blue and black.

Gemstone grade coral is red, pink, and orange-red.

Red coral is due to its growth process to absorb about 1% of iron oxide in seawater, black coral is due to its organic matter caused by.

The surface of coral has colorful fluorescent pigments that can adjust the light, which has an important role in the influence of coral symbiotic algae and in the adaptation of coral to different environments of light and dark.

Corals have their own unique requirements for growth environment:

1. Water temperature

Coral growth of water temperature is about 20 ~ 30 ° C.

Tropical sea areas, this optimal water temperature occurs in winter and spring, so many scholars believe that the fastest coral growth in winter.

2. Salinity

Reef-building coral grows in the salinity of 27 ~ 40 seawater, the best salinity range is 34 ~ 36.

South China Sea salinity is 34, is the best salinity range, Hainan Island coast has fresh water injection, salinity is slightly lower, about 32.

3. Water depth

It is generally believed that the water depth range for reef-building coral growth is 0-50 meters, and the best water depth is 20 meters to shallow.

Many scholars believe that this is actually the depth required for photosynthesis with the reef-building coral symbiotic algae.

4. Light

It is also the need for photosynthesis of the bug yellow algae, general tropical light is strong, long, the average light rate in more than 50%, conducive to the development of coral reefs.

Mediterranean Sea and the coast of Portugal to Senegal, the sea is growing in the extremely rare red coral.

Red coral is born in shallow sea 20 meters to deep sea more than 300 meters depth, in shallow sea growth of red coral even if there are hard skeleton.

When the storm waves swept, inevitably there will be broken branches washed up on the coast, was picked up.

Also because of this, the Mediterranean red coral become the first to be collected and sold gem coral.

The tip of the branch of the red coral group will cut off a small section.

When this small section of coral branches stuck in the crevices of the rock wall successfully fixed, will be here "root", and eventually grow into a new red coral "tree".

It takes about 30~35 years of growth period for red coral to reach the minimum size for commercial fishing (root diameter 7mm).

Due to the preference of some people and the high price of profit, red coral has been plundered and poached in some areas.

Today, red coral populations in most of the Mediterranean Sea are difficult to recover in the short term and have caused incalculable damage to the local marine environment.