83 is fine so long as it is always between 82-84. You don't want your temperature going up and down and up and down, day after day.
For example, if it is 78 in the morning before the lights are on, and then it is 86 when the lights turn off at night, this is not a good situation. When the temperature fluctuates in a range of more than four degrees over the course of one day, not only is their stress on your creatures from that, but you also have to remember when the temperature changes significantly so does your specific gravity which is even more added stress. A tank with 35 ppt salinity will have a specific gravity of 1.026 at 78 degrees, but at 86 degrees the specific gravity will be 1.023-1.024.
:joy: