I've had two unexplained coral deaths recently, so it's possible this is related. The affected coral isn't dying yet, but it's killing patches of zooanthella. If you look at the second pic, there's a bigger dead spot where I scraped off the puffs - I'm still not sure what to call it. Not all those spots are where the polyps are, that's where the filaments come from, in my experience. The filaments should retract eventually, right? I've been noticing these spots for weeks now. I've been keeping a close eye on my other corals since I noticed this, and they were fine. But now I've found a couple more corals with the same issue.
What can I do to address the chemical cues, or test that theory? I've done some big water changes, 20% over the past couple of weeks, but I haven't seen any change.
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