My tank usually sets at about 77 Degrees, with the air on it will dip just slightly below that. I got my heater on a schedual to come on for two hours every 9 hours, but I have it up higher to help the bacateria grow since my last tank broke I had to replace it and begin a fish cycle. Even in my other tank I had the temp bobbing around the 80's. I have 5 guppies and a pelco and they all liked the warmer water than the chill at 77's. I would just watch your fish and experiment a bit and go for what they seem to feel comfortable with. My tank right now is 83-84's. They are doing just fine.
36 Gal. Bow, Current Project
-Scene: Silk Plants/Eco-Complete/Natural Driftwood-Equip: Marine Fliters/Penguin Powerhead/120 Watt Heater/Plain Fluor(Sundail T5 Soon)
-Swimmers: 5 Gups Male/One Pelco(More Gups And Tetras Soon)