Whereas humans can take great temperature variations, fish and corals cannot, and will die if you do not adjust the temperature of your tank correctly.
Don't go from a present 82 deg to a new temperature of 76 deg in a matter of hours.
Too large a submersible pump, or too many power heads will raise the temperature several degrees, perhaps several too many.
If you cannot solve your temperature problem by changing pumps, or by installing fans in the lighting hoods, you may be in a quandary that can only be resolved by installing a cooling unit.
Rather inexpensive coolers can be made using a small second hand freezer.