How Do Corals Eat?

Photosynthesis

Corals contain endosymbiotic relationships with microscopic algae called zooxanthellae. These algae live inside coral cells and are capable of photosynthesis, meaning they produce nutrients for the corals such as carbohydrates and amino acids. In return, the corals provide the zooxanthellae with shelter and the substances necessary for photosynthesis.
The process of photosynthesis in corals occurs in several stages. At first, the energy from the light is absorbed by the chlorophylls contained in the zooxanthellae. This energy is then used to carry out chemical reactions that lead to the production of glucose.
Oxygen and by-products are also released during photosynthesis. It is worth remembering, however, that the photosynthesis process in corals is particularly sensitive to changes in conditions in the aquarium, such as temperature fluctuations or water pH. Under unfavorable conditions, zooxanthellae can be damaged and photosynthesis inhibited, which in turn can lead to weakening or even death of corals.
The way corals feed through photosynthesis is able to cover most of their energy needs. Photosynthesis provides them with the right amount of energy to survive. However, in order to grow, the coral needs extra energy.

Food filtration

Corals have polyps, which consist of a cylindrical body surrounded by a mouth. The polyps can form colonies of various shapes and sizes. Each polyp has the ability to produce spines and slime that aid in catching food and protecting the coral from predators.
The spines are small protrusions of protein that grow from the body of the polyps. They are used for catching food and for defense against predators and competitors. They are flexible and mobile, which allows coral polyps to react quickly to environmental stimuli. The spines are also covered in a sticky substance (mucus) that helps attract tiny organisms.
Mucus is secreted by coral polyps in response to a stimulus related to the presence of food in the water. The mucus covers the spikes of the polyps and forms a net that attracts and holds the tiny plankton and then transports it to the digestive cavity of the polyps for further processing.

Predation

Some species of corals such as: trachyphyllia, fungia, scolymia, heliofungia and many others are predatory and prey on small organisms such as shrimps, small fish and other invertebrates. These coral species have special organs, such as valves, that help them capture and digest their prey.
The valves are movable protrusions that are found on the bodies of some coral species and are used to catch prey, they are shaped like a hook and are very effective at catching small organisms.
After catching the prey, the digestive process begins. Digestion takes place in the digestive cavity, inside the coral’s body. Corals use enzymes to break down food, which is then absorbed into their tissues.
Other corals that feed predatory and like to be fed are: Fungia, Trachyphyllia, Heliofungia, Catalaphyllia, Euphyllia, Scolymia, Acanthastrea – mainly LPS.

Summary

In this article, I described three different ways of feeding corals. When we decide to buy a given coral, we should know how to properly provide it with food. The key to success is, of course, the lighting of our tank, but as the article shows, some LPS corals are worth feeding with frozen shrimps or smelts. When choosing non-foto corals, you should provide them with food for filtering, and if their specificity allows it, they should also be fed with frozen food.