Here part of an article I found Sen. Congrats on the coral.
Aggression
Today, more attention needs to be given to reducing aggression, since many of the newer species of corals that we are now keeping are much more aggressive. This aggression has also become more of a problem as a result of our being more successful at keeping corals in general. That is, as we have become more skilled at actually growing coral colonies, our corals are growing to larger sizes. As the size of these corals increases, so too does their proximity to each other, and as a result, more of their aggressive nature manifests itself. Thus, while their aggressiveness was hardly observable and not a problem when they were a small, three inch colony, their effect on neighboring corals becomes dramatically noticeable when they are twelve inches across.
Types of coral aggression
Corals have developed several specialized mechanisms for protection and competition with other corals. These include sweeper tentacles, mesenterial filaments, and terpenoid compounds (Ates, 1989).
Sweeper Tentacles: Sweeper tentacles are the most common defense mechanisms in the hard corals, and also occur in some soft corals. Specialized stinging cells called 'nematocysts' are present in these tentacles and can attack a competing coral and literally "burn" it to the point of either killing it or severely damaging it. The length of these sweeper tentacles is not correlated to the length of the normal coral polyp and may, in fact, be many times longer.
Mesenterial Filaments: In addition to sweeper tentacles, several hard coral species can produce mesenterial filaments (also termed mesenteric filaments) from their stomachs. Corals of the genera Favia, Favites, Scolymia, Pavona, and Cynarina all have this capacity (Chadwich, 1987). These filaments can kill or devour other coral polyps through a process similar to digestion. Some corals even have the capacity to produce both sweeper tentacles and mesenterial filaments, enabling them to fight a battle on several fronts (Wallace, 1984).
Terpenoid Compounds: The soft corals generally compete with the hard corals by releasing 'terpenoid' or 'sarcophine' compounds into the water to injure or impede the growth of neighboring corals, and then overgrow these impeded individuals in a process called "allelopathy" (Delbeek and Sprung, 1994). Like their name implies, these compounds are similar to turpentine in chemical structure and in most instances, are just as toxic. By releasing these compounds, the soft coral injures these neighboring stony corals and can thus grow above them, eventually blocking out the light that they are both dependent upon and thereby killing the underlying hard coral.
Use correct spacing
While a miniature reef does not contain the great diversity of life that an actual reef does, provisions should still be made to try and minimize the aggression among corals. This can be accomplished by providing adequate spacing and reducing tip over potential. When setting up a tank, adequate space, which is invertebrate free, should be given around each coral head.
Hard Corals: For LPS corals, this zone should be at least 15 cm in all directions, as sweeper tentacles have been reported to be at least this long (Sheppard, 1982). The distance between SPS corals does not need to be as great; a distance of 5-8 cm is usually sufficient. However, it should be noted that these are the fastest growing of all corals, so extra space should be allowed for this. For this reason, I suggest that a buffer zone of 30% of the coral colony's size be used when originally placing the corals in order to allow for growth. This may seem extreme and may initially make the tank look sparsely decorated. However, in a well-designed and maintained reef tank, this space will be almost completely filled within the first year simply from growth. If growth space is not provided, there will be a constant need to prune corals lest they burn and kill one another.
Soft Corals: For the most part, the space between soft corals does not need to be as great initially, since soft corals do not burn each other to the same degree as the hard corals do. Consideration in placing soft corals needs to take into account:
A faster growing coral will overshadow a slower growing coral and eventually starve it out for light.
These corals should be positioned so that their mucous and terpenoids do not come into direct contact with their neighbors. That is, these corals will do the least harm to other corals if the water movement in the tank is such that after the water moves across them it flows down an overflow and into a sump where the harmful compounds can be removed with either skimming or carbon.
Minimize tip over potential
Tip over potential is the likelihood that one coral will tip over and land on another coral, and as a result, burn or be burned by the other coral. The burned area becomes infected and consequently, the whole colony dies. Tip over is particularly troublesome for SPS corals, which usually arrive unattached to anything. Therefore, when placing these corals on a live rock structure, use a dab of waterproof epoxy to hold them in place until they encrust over the area themselves. An alternative is to use rubber bands or plastic cable ties to anchor the colonies in a less permanent manner.
