I’m no scientist but this seems obvious, as someone who’s had a saltwater aquarium and done maintenance myself.

I didi’t even bother with coral, the closest I got was an anemone. I had the tank in balance for about a year with a great ecosystem that all but took care of itself with minimal water changes. Then one long weekend vacation the power went out for several days and it was enough to throw things out of whack. I tried for a year to carefully get it back and never could.

Until we can stop/control climate change, it is a losing battle and even then, it will be difficult if not impossible to get them back to what they once were.