It depends, some SPS corals can touch, while other corals cannot. Some SPS coral species do not mind a close neighbor, allowing them to coexist, while others will often fight until death through chemical warfare. The main factor that influences this, is the type of coral it comes into contact with. 

Corals naturally grow into and on top of each other, just take an established coral reef ecosystem in the wild as an example. If you have ever been scuba diving or snorkeling, you would have seen that corals do not consider “personal space”. As corals grow, they often fight it out through chemical warfare and encrust on top of each other as they compete for precious real estate. 

When adding SPS corals to your reef aquarium, it is recommended to place them in areas where they cannot touch each other. This is because some corals can be extremely aggressive, often stinging other corals with their nematocysts located in the coral’s polyps. However, some SPS corals do not mind a close neighbor and can coexist side by side. In this article we will cover if SPS corals can touch, and what happens when/if they touch each other. 

Can SPS Corals Touch Each Other?

Although some SPS coral species can touch without creating a war zone in your aquarium, it is best to not let them touch each other if possible. 

As corals grow, they branch out and encrust on nearby surfaces, which can sometimes be another coral. This means that when other corals get in the way, they can sometimes touch, so is this something you should be worried about? 

Peaceful corals can sometimes be kept close to other corals of the same species. Always monitor the coral’s temperament when adding it into your reef aquarium and research the SPS coral’s aggression level to determine what corals they can be kept close to. 

Remember that corals are animals, not plants, so they have different personalities, much like ourselves! If they have a calm temperament, they should be fine being moved closer to other peaceful corals. 

Montipora corals are probably one of the least aggressive SPS corals, while Acropora millepora corals are the more aggressive type. Usually, as long as you keep the same species of SPS coral next to each other it is ok for them to touch, ensuring they are from the same lineage. However, some peaceful SPS corals from different lineages are known to be kept close together successfully, some even touching without harming one another. 

What Happens When They Do Touch?

In a reef aquarium, there is usually a kind of hierarchy of "coral power". When SPS corals touch, they can be unpredictable. Sometimes one coral will win, but sometimes neither of them take any damage from touching and continue to grow over one another. In the wild corals naturally fight it out, which is what some aquarium hobbyists allow nature to take its course. They simply will let nature take its course by allowing SPS corals to touch and observe them. 

Since SPS corals stand for small polyp stony corals, they generally do not produce long sweeper stinging tentacles. If SPS corals do touch each other in your reef aquarium, you are likely to get a bit of warfare at the point of contact, but it doesn’t always result in killing the coral. Usually, the most dominant SPS coral (mainly Acropora corals), will keep growing whilst the weaker one loses parts of its body that are touched.

Some SPS corals like Acropora will battle with other corals in the aquarium for space. The coral that loses will usually receive serious tissue damage or its tissue can sometimes die.

Branching SPS corals like Acropora contain mesenterial filaments that contain the specialized stinging cells, used for feeding and fighting. So when other corals come too close to Acropora corals, Acros will fight for dominance by physically attacking neighboring corals, damaging and digesting their tissues, often resulting in tissue necrosis. Again, some corals will not resort to using their mesenterial filaments, happily growing into or just around each other.

SPS corals from the Pocillapora family, commonly known as Cauliflower Coral, are an example of SPS coral that can grow into each other. They do not damage each other, but one will usually be dominant, outgrowing the other. 

Some corals will show signs of stress if their neighbor is getting ready for battle. If you notice brown spots on the coral, or they are refusing to open or extend their polyps, they are likely telling you to separate them from their aggressive neighbor. 

When you add corals, you should position them so they have plenty of space to grow before they will come into contact with another coral. If you notice them almost touching, most hobbyists will trim them to avoid conflict, much like trimming your hedge in your backyard. These trimmings are called coral frags, which you can place elsewhere in the reef aquarium to grow another coral colony. Some people will move a coral to a safer area of the aquarium, but sometimes this can kill the coral from elevated stress levels. As mentioned, some people do leave it up to the corals to fight it out, but this could sometimes result in the weaker coral dying. 

Conclusion

Some SPS corals can live in harmony, coexisting with one another, however, some corals may start warfare if they get too close or physically touch. Usually, SPS corals of the same species will do fine being placed close to each other. 

If SPS corals do start fighting, one will usually win which can kill the weaker coral. Before they touch, it is recommended to trim your SPS coral, which is also a great opportunity to add a new frag into your reef aquarium!

If you have any questions regarding which corals can touch, or the SPS corals we have to offer, please feel free to contact us, we are always happy to help!