Temperature is always a hot debate... Some people have been very successful keeping their tanks as low as 76F (seems low to me) and others have also had no problems keeping their tanks as high as 86F (seems high to me).
The people on @ 76F claim that too high of temperatures limit oxygen levels in the water and that both bleaching STN/RTN are more also linked to temperature. This may or may not be a totally validated argument. but the only time i have ever had a coral STN/RTN was during summer, i had multiple problems and couldn't target the exact causes.
The people @ 86F have provided evidence that many reefs around the world rotinely reach temps well beyond 86F and the oxygen saturation level isnt really an issue. as they explain it fish adapt to their environment like humans, sure its hot the first time you go to Hawaii but if you live there long enough you need a sweater on 75F+ nights. Meaning that fish don't maintain a faster metabolism and so on based on temp. They also claim that the oxygen saturation level difference between 10 degrees isnt so drastic, and that even in an overly stocked closed system would mean a 10 to 15 min difference of fish survival with out flow.
well that's what others say. Me, well i have a fan over my sump, and it kicks on at >81.9F and my heaters kick on at < 80.9 in the summer i will turn up my haters to limit the difference a little more as ambient temp heats my tank up to 82.8F (hottest this year) i try to maintain as small of a temp swing as possible. 2-3 degree swing is good 4-5 is pushing it and anything >5 is bad news IME.
