WHAT CORALS NEED MOST

Corals are very sensitive organisms and environmental conditions need to be just right in order for them to flourish. Corals need:

Abundant Sunlight

Reef-building corals cannot survive without sunlight. Although some can be found at depths of 6,000m (20,000ft), corals can generally only live in the relatively shallow water of the oceans where light can penetrate. This means that the majority of corals do not grow below 45m (150ft).

Warm Temperatures

Corals can only live within a narrow temperature range from around 16°C - 29°C (62°F - 85°F). This explains why corals thrive in the warmer waters of the tropics.

Low Nutrient Levels

Corals are adapted to live in oceanic water, which contains very low levels of nutrients. Nutrients, which are needed by all living organisms, are found in food and dissolved in water. They can be washed into the sea in rainwater draining from the land. Too many dissolved nutrients can upset the natural balance of life on the reef, creating conditions that favor other fast growing organisms such as marine plants and sponges.

Clear Sediment Free Water

Corals prefer clear water with low levels of sediments. Sediment is the name given to small particles of earth or rock and sand in the water. Sediments can bury corals, blocking out sunlight and choking and killing them. Corals prefer to live in areas with some wave action as this helps supply them with food and oxygen as well as keeping them free of sediment.

Salty Water

Corals are adapted to live in seawater. Oceanic seawater has a salt concentration (salinity) of around 35 parts per thousand (‰). Although some corals can live in areas with salinities of up to 42‰ most corals cannot grow in fresh water or very salty (hypersaline) water.

Hard Substrate

Corals need a solid foundation (substrate) to attach to and cannot successfully colonize unconsolidated substrates such as rubble or sand. Where the substrate is unstable young corals colonies will be crushed and killed by wave action and