How Do Corals Eat? A Comprehensive Guide to Coral Feeding

For anyone who is fascinated with the strange nature of coral, chances are, you’ve contemplated how they survive. Do they absorb sunlight like most other plants? Do they obtain nutrients from the water? 

If you’re an ocean aficionado in search of biology food for thought, or if you’re considering growing coral at home, then here’s a complete guide to coral feeding and nutrition.

What Are Coral? 

Ocean lovers might remember a time as a kid reading Jules Verne and picturing coral monsters with mouths filled with razor-sharp teeth. If you’ve ever been scuba diving or watched Planet Earth, you might have thought about the absurdity of that image. That image isn’t entirely wrong. 

How Do Corals Eat 

Coral comes in many shapes and sizes, but they are all living animals. If we look at them, it doesn’t look like they have mouths and a digestive system, but they do. And they need to feed themselves regularly. 

Corals are sessile, which means they cannot move to obtain their food. Instead, they have tentacles that reach out into the ocean and snatch unsuspecting ocean particles such as zooplankton. 

How large corals’ prey is, depends on the size of the coral itself. Like most living creatures, corals have specific times which they like to feed (humans do too, think breakfast, lunch, and dinner). Coral isn’t much different except for their feeding time depends on zooplankton. 

Zooplanktons rise to the surface of the ocean around sunset, and it’s then when coral fills its belly. Coral also feed when zooplanktons retreat from the surface at dawn. 

How Do Corals Tentacles Work

In addition to their tentacles, corals have an outer mucus layer that aids in transporting nutrients to their digestive system. Some corals don’t even need tentacles and only use the mucus membranes to transport nutrients to their gastrovascular cavity. 

What Do Corals Eat

Corals get their nutrition from different sources. Many corals use their tentacles like fishing nets that catch dissolved organic matter (DOM). DOM consists of organic molecules that float in the ocean. These organic molecules come from many places, including ocean animal waste and decaying animal waste. 

Corals also use sediment as nutrition. They trap floating sediment with their tentacles and extract the organic molecules from the deposit, such as amino acids, sugars, and lipids. Sediment can also contain bacteria or protozoa (single-celled organisms that contain many nutrients.)

Can Corals Bite

Corals cannot bite, but some corals can undoubtedly sting. Many corals have a predatory mechanism known as nematocysts. Nematocysts are stinging cells located in corals’ tentacles.

These stinging cells are very similar to those of jellyfish. An example of a coral that possesses these stingers is fire coral, which produces a paralyzing sting. 

The three types of nematocysts

Glutinant- Glutinants have a sticky surface that stings prey and causes it to stick to the tentacles. 

Penetrant- Aptly named stingers that act as tiny harpoons and penetrate the exoskeleton of zooplankton. 

Volvent: The cowboy of tentacles that has a lasso-like structure that captures prey in tentacles. 

Living Together In Food Harmony 

Corals can also derive nutrients from a symbiotic relationship with certain types of algae. Zooxanthellae, whose pronunciation is not very important, is the algae that corals bond. 

Corals can have one of three different types of symbiotic relationships with algae.

Corals and algae can have a mutualistic relationship where both the coral and the algae benefit. The coral and algae can have an endosymbiotic relationship where the algae live inside the coral, and they can have an obligate relationship where the algae are obligated to live with the corals, or else the coral dies.  

Do Corals Use Photosynthesis

In most cases, corals do not directly use photosynthesis. Instead, they obtain the byproducts of photosynthesis from the zooplankton they feed. 

In cellular respiration, the coral obtains ATP and gets its life force. 

Feeding Coral at Home 

Now that you know all there is to know about how to feed coral in the open ocean, how do you feed coral in a fish tank? The answer is very similar to how they feed into the sea.

Until recently, keeping coral in a saltwater aquarium was next to impossible. It was difficult because there was no way to control the water quality well-enough to protect the coral from toxins such as nitrates and phosphates. Luckily the science behind aquariums caught up. 

Direct Feeding 

If corals have larger mouths, they usually eat larger prey. Examples include brain coral, elegance, and Plate corals. 

Examples of direct feeding include feeding bigger corals diced fish, frozen plankton, phytoplankton, krill, pieces of shrimp, squid, or clams. Do not overfeed corals. Overfeeding corals can cause a build-up of phosphates and kill the corals. 

Also, corals need a current to flush their digestive tract, so take care not to keep corals in stagnant water, or else they will die. 

However, while feeding your coral, you’ll want to turn the current off. Gently target each coral. Feeding coral in the beginning and the end of the day keeps them in a feeding routine they would follow if they were in the ocean.

Drizzling some food in the tank before feeding each coral can prepare your corals for feeding. You can also try a polyp lab reef booster to stimulate your corals for feeding time. 

Owners should feed their corals several times a week. After the corals adjust to the feeding schedule, they should become more responsive and add color. Usual benefits from consistent feeding schedules include polyp extension, puffier body tissue, increased vibrancy, and increased growth (compared to unfed corals).

Indirect Feeding 

Some corals can survive off the fish who live in the tank. They don’t eat the fish, thank God, but they survive off the scraps the fish leave behind. Bacteria that fish do not consume is a viable food source for corals. 

Different Strokes for Different Corals

Researching how corals eat is the best way to ensure you’re feeding your coral the right food. A food chunk the size of your fingernail is of great value to many Large Polyp corals but is too big for a Zoanthid. 

Owners should research how corals eat in the ocean to decide the best practices to use while keeping corals in the aquarium. Click here to discover more exciting facts about aqua life!