Marine aquarium with corals

Do I need to feed my aquarium corals?

The question about the need to feed corals is as old as the hobby itself. It might seem that everything has been said about it but the topic always returns like a boomerang to online forums or Facebook theme groups. Everybody seems to know that corals are animals and must eat, but the feeding itself leaves a lot of doubt. Not surprisingly, many beginner aquarists are reluctant to feed corals, or ignore this issue, probably due to the lack of knowledge. For those of you who expect a simple answer to the question “Do I need to feed my corals?”, let me say briefly: yes, feed them!

Why do you need to feed your corals?

For animals food is both a source of energy and building blocks used mainly for growth. Higher animals in the wild have no problem with excess food, because it is regulated by simple population control mechanisms and supply-demand type relationships. Excess food will be used to increase the population of a given species. The shortage of food is a much worse scenario. Deficiency of food not only limits the development of offspring, but also negatively affects existing individuals, causing malnutrition or even death.

In corals it is different. The food itself is, of course, necessary for the same reasons as above. However, corals are much more resistant to changes in access to food. Their physique is very simple and they adapt to change much more easily. The vast majority are able to enjoy the benefits of photosynthesis thanks to the presence of symbiotic single-celled algae (known as zooxanthellae) in their tissues. Let set aside the discussion that these are in fact protists and not algae. The important thing is that they are autothrophs, like plants. This means that they produce sugars through access to light, carbon dioxide, water and mineral salts. The excess of these sugars is shared with the host, that is, the coral.

Feeding corals
Zooxanthellae living in coral cells share produced food with their hosts.

Remember that zooxanthellae alone are not enough

Along with sugars, corals can receive small amounts of amino acids and fatty acids. Unfortunately, while there are quite a few sugars, which is enough to cover most of the corals’ energy needs, zooxanthellae do not provide enough building materials for coral growth. In result, corals need to take nutrition from other sources just like other heterotrophic animals. The second issue is that the vast majority of corals are colonial organisms that, given access to food, can theoretically grow with no end. In practice, however, this is impossible due to the emergence of growth-limiting factors. These include access to light, weight gain and natural factors such as storms and tsunamis.

In growing higher animals, such as fish, malnutrition can lead to abnormal development and organ dysfunction, resulting in premature death. With limited access to food the colony of corals will simply slow down or even stop growing. Meanwhile, the polyps themselves will begin to maximize symbiosis with zooxanthellae as a food source.

On coral reefs, access to food is mostly uninterrupted, as ocean currents deliver nutrient-rich water to the shallows. Corals that end up in the aquarium must feed the same way they did in the wild. Therefore, let’s not forget to feed them regularly. However, the process of feeding corals in an aquarium is a challenge, as you will learn in future posts.

Bartek Stańczyk

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