How hot is too hot?

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Today my heater malfunctioned, my temp is up to 84 degrees. All of my fish corals and anemones look OK.

I have ordered a heater and controller unit but it will be awhile before it gets here.

In the meantime I can make do with spare heaters or adjusting the current heater.

Usually my temp runs around 81 degrees.

Where is the danger zone for my fish and corals? I am assuming over 85 degrees and I will be in trouble.