Very careful attention must be paid to the placement of corals in the reef tank visa coral compatibility. Many corals are extremely aggressive hunter/feeders and can inflict severe damage on non-compatible tank mates if not properly separated from them. 

Depending on the species and particular circumstances, corals may employ one or more of the following aggressive mechanisms:

  • Rapidly overgrowing neighboring invertebrates—i.e., actually growing directly onto the neighboring colony or extending over it and preventing it from receiving life-sustaining light
  • Stinging neighbors with nematocyst-laden tentacles
  • Extruding digestive organs (called mesenterial filaments) and essentially digesting the tissues of adjacent corals
  • Exuding toxic chemicals (e.g., terpenoids) into the water to kill neighboring corals or impede their growth

What can you do to counteract these hostile tactics?

  • Research your corals thoroughly before you buy them - A little modest research on the characteristics of different corals will reveal all kinds of vital information regarding their relative aggressiveness/noxiousness. For example, Sarcophyton leather corals are notoriously toxic and various Euphyllia corals are known to produce long, stinging “sweeper” tentacles. Such details must be taken into account when choosing which species to combine and how to situate them in your tank.
  • Space your corals out properly - When placing specimens, allow more room between them than you think they’ll eventually If the tank looks sparse initially, that’s okay. It’s better to have a smaller number of specimens with plenty of room to stay clear of each other’s tentacles than to have a larger number growing on top of one another and in a state of constant warfare.
  • Isolate rapid-spreading corals - Corals/polyps that form encrusting mats and grow rapidly outward onto adjacent substrates, such as green star polyps and certain zoanthids, may need to be isolated to a single, separate rock—an island, if you will—to keep their growth in check and prevent them from irritating or overgrowing cnidarian
  • Maximize water movement - Brisk, turbulent water movement, which is beneficial in many reef- aquarium settings anyway, will help prevent toxic chemical compounds from concentrating around any particular specimen. Keep in mind, however, that not all sessile invertebrates appreciate a high level of current. Some, such as Discosoma mushroom polyps prefer very low levels of water movement.
  • Employ a protein skimmer, chemical filtrants, and copious water changes - Vigorous protein skimming and chemical filtration with activated carbon will help remove/adsorb the byproducts of coral chemical warfare. And, of course, you can add the removal/dilution of these toxins to the many virtues of regular partial water.



  • The rule of thumb here is that if your coral has tentacles, chances are it is one of these aggressive species (including, but not limited to Catalaphyllia sp., Galaxea sp., Euphyllia sp., Goniopora sp., Heliofungia sp. Fungia, sp, etc.), however, many “fleshy” LPS corals like Trachyphyllia sp. and Lobophyllia sp. can also extend feeding tentacles and sting their neighbors. Anemones are also obviously aggressive “stingers” and should be placed sufficiently far from corals so that their tentacles cannot inflict damage.
  • Although mushrooms and polyps are relatively harmless, there are some species that can be semi-aggressive to their neighbors. Same thing applies to “softies”, some of which can secrete toxic chemical compounds from their tissues.
  •  Take a good amount of time to research the species you want in your aquarium to see how aggressive they are! Separate all aggressive species sufficiently from their neighbors. It won’t be difficult to see if they are far enough away because if they are not you will soon notice necrotic (dead) spots on the “victims” in the areas closest to the “stingers”. Also, make sure to re-evaluate the separation as your corals grow and encroach upon each other.
  •  A little precaution and some constant attention will yield invaluable results and allow you to maintain and enjoy a successful reef aquarium for years to come.