What is coral aggression, and why does it happen?
Corals aren't inherently aggressive, but they can exhibit aggressive behaviour under certain circumstances. This behaviour is primarily seen in competition for space and resources, particularly when corals are near each other.
Corals use various mechanisms to compete with each other, such as extending sweeper tentacles armed with nematocysts (stinging cells) to ward off or attack neighbouring corals. This aggressive behaviour helps corals defend their territory and maximise access to sunlight and nutrients. These interactions are a natural part of the dynamic and competitive ecosystem of coral reefs.
As you’ll see on our website, we even list how aggressive some corals are! But don’t worry. You can rest assured that with a proper environment, care, and equipment, your corals will flourish in your tank. So, in this blog, we’ll look at the types of coral aggression, particularly found in reefs, which provides context to their aggressive behaviour.
Types of coral aggression:
Overgrowth
Some corals just grow a lot quicker than others and may out-compete neighbouring corals for space by growing over them. This blocks the one critical necessity that they need: sunlight. Which effectively starves the surrounding corals.
Sweeper tentacles
Certain species of coral, including many of the LPS variety, have extended sweeper tentacles. These tentacles sting neighbouring corals and fend off competition. One sting will most likely not kill the surrounding corals, but if multiple stings occur, this can damage or kill other corals.
In addition to defence and competition, sweeper tentacles can be used to capture small prey organisms that come into contact with the coral. Once immobilised by the stinging cells, the prey is drawn towards the coral's mouth for consumption.
Chemical compounds
Soft corals can also be defensive toward other corals. When threatened, they may release toxins into the surrounding water or inject them into predators through stinging cells. Palytoxin can be toxic to both fish and humans, so if you keep Palythoas or Zoanthids, it's important to manage your tank and ensure there’s minimal contact.
Mucus
Many corals have a layer of mucus covering their surfaces. But in some cases, corals may increase mucus production. This chemical warfare will be a response to stress or competition if they are trying to defend their territory.
What to do about coral aggression?
It’s important to keep a close eye on your tank. If you spot any of these acts of aggression, there are multiple steps you can take to stop them, including separating the aggressive corals by creating physical barriers or providing more space between corals. Adjusting your tank and creating a more balanced environment can help. You can do this by adjusting the lighting and flow of your tank. Always make sure to do regular water testing; poor water quality can also increase aggression.
We're happy to help if you would like to talk to one of our experts about coral aggression, your tank, corals in general and all your reefing needs.