If the conditions that bleached the coral doesn't improve, the odds are much lower that it will survive bleaching. This is one reason why rising sea temperatures are a disaster to many corals. A few corals like the warmer temps, but what happens is diversity on the reef is impacted. As a diver and reef keeper I am also a environmentalist because I see the effects right in front of me.
In the aquarium, if you improve the conditions that bleached the coral, like too much light exposure, fixing the problem will give the polyps a fighting chance to repopulate the algae. That's if it isn't disease or a factor that kills the polyps off.
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