LionFish says......
My current 20 gallon reef seems to stya round 80 degrees on average. This seems to be fine with the Black-Cap Basslet and 6-line wrasse. Although all my larger tanks are around 78 degrees which I like more because in the summer the tank rises about 2 degrees on hot days so it won't exceed 80. My 180 will be kept around 78, too.