I don't believe it to be true that preventing these things causes more harm than good. And no not really, these pests can thrive in a mature reef tank. Ever been to an lfs? Notice how their age old systems typically have these pests? Corals also do not outcompete algae. In real reefs, algae chokes out corals if something caused a major disturbance in their predator's presence. And no, most of these problems don't necessarily come on coral. Coral and rock are practically the same thing in a reef tank except rock has way more places for pests to live and hide. Also, no one is trying to keep a sterile reef. I am not sure how people equate little to no pests as sterile as they have nothing to do with each other. We need to stop comparing reef tanks to normal reef ecosystems because they simply are not. We pick and choose creatures from all over the world to live in a tiny box that is nothing like an actual reef. I'm going to stop talking about this here though since I don't want to hijack the thread topic.