And with all due respect, this is why I normally try to avoid this subject. People have very strong oppinions on this topic, including myself.
There are many animals we keep that are not appropriate to be kept together. Many people don't know the potential harm that can come from mixing some of these animals. It is understandable for these people to make mistakes and mix animals that harm each other. The only time I have a problem with this is when people knowingly place animals together that can harm each other. If someone knows that clown fish can harm Elegance corals and they decide to place them together in an environment where this harm is likely to take place, I find this irresponsible. We have control over our aquariums and what we keep in them. I believe it is our responsibility to provide each of our animals with the best environment possible, or at least strive for this goal. We would not put two Siamese Fighting Fish/Bettas in the same bowl, then sit back and say there is nothing we can do to stop them from killing each other. Why is it any different to allow clown fish to use Elegance corals as a host and watch the corals health slowly deteriorate? Saying I can't stop this behavior does not work.
Mike posted this question because he noticed his Elegance corals expansion diminishing after the clowns moved in. This is exactly what happens. This coral began to show the bad effects of this relationship in less than 3 days. I believe that saying "don't let them do that" is good advice, especially in this case. What should I have said?
Don't get me wrong, I am not criticizing people that allow this to take place. I have done it myself, more than once. I believe that many people simply don't realize the potential harm this can cause. I kept a pair of clowns in a very large Elegance for well over a year. It took many years and several attempts before it finally sunk into my head exactly how bad this relationship can be.