Mine run at 78-79. Everything is growing well.
Back when I lived in PA I had my 20L with nothing but softies and some lps like an acan, trumpet, and a small goniopora. No AC and just a fan blowing. Over the 5 months Feb-July it ran from 75-77 in the spring to 83-85 in the early summer and 84-90 in June before I moved. All zoas grew throughout and the acan went from one head to 7. Trumpets never grew. Goniopora nearly doubled in size. That was my first tank haha. I ended up losing most during the move but all the fish are still around happy and swimming.