Hi Matt - just something else as well - I agree with the wanting the temp to stay constant - BUT, take into account that the water temp also changes on the reefs in the sea as well - as long as the change is NOT TOO rapid, and not too high - and as long as the temp does not stay high for too long either.
Alan made a very important note: the higher the water temp, the less oxygen in the water - this is a major problem..... so ensure that you have oxygen in the water for the life-stock (power-head that churns the water surface)....