I can't remember what I keep mine at, but I think he's usually at or around 82. Smack dab in the middle of the green on my glass therm (before my fiance broke it!!)
for shoals i keep it at 76-77 to help reduce aggression and for single species i keep it at 82-84 to get them moving more which increases their motabolism so they hopefully eat more and get bigger faster.
by the way,i do this as least as possible. im talking like summer vacations and christmass. thats basically it. not good to change metabolism too often...i know