Anything above 84 can kill your fish. Remember to keep salt in the tank to keep down the fungus in these warmer tanks. Also note more temp equals more aggression. The increase in metablism increases their search for food which in turns makes them aggressive and very hungry.
Aquarium salt i just give a good dash after changing water, 1 teaspoon per 5 gals when sick. And i keep it at 79 unless sick or injured. I have never noticed a difference in them at higher temps, but that is just me.