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Edit note: edited for atrocious spelling, no content change. My apologies for not proofing the post-tdw)
If you mean "will they send out sweeper or mesenteries to attack other corals ?" no they do not do this, but if you mean, "will they release chemicals (allelopathy) into the water column?" yes they will. They are of moderate toxicity to other octocorals, although there are some spp. that will respond to their presence by pulling in their pinnules, etc., but for the most part, they are only of moderate aggressiveness to other octocorals; stonies, on the other hand, may have major interactions with colts, often resulting in unexplained failure to thrive and/or slow or stunted growth of
hermatypic corals. Colt corals get quite large over time, so plan for at least 6 to 8 inches of space downstream from ANY
stony corals (better to not have them in the same water column), or perform 10% weekly water changes and run carbon 24/7 and skim heavily. You will need to separate colts at least 4 to 6 inches from any other octocorals as well, although many conspecifics may be in constant contact with each other in the wild. If you have to cut the tissue of these creatures, make sure to do this OUTSIDE of the tank's water column (in a separate bucket), as cutting releases many of the allopathic substances into the water column.
Members of
Nephthea, Sinularia, or
Capanella genera of octocorals produce many toxins that give them some means of competing with stony corals for space on the reef, even though the biotopes for most reef top species of stony corals are not preferred environments for most octocorals. Mixed stretches of reef ridges in the wild usually give way to either monospecific stands of octocorals or areas of mixed octocoral genera bordering areas of similar population dynamics for stony coral stands when conditions permit.
hth
