I do really appreciate everyone’s help.
So I guess if I would’ve readdressed the question appropriately
You do understand that’s equivalent to saying the price of gold has not changed in two years. Just a unit of measurement has changed.
What Randy is saying is that the salinity is the amount of dissolved salt in the water - the actual amount of dissolved salt in your water doesn't change with the temperature, but the amount of it detected by the tool used to measure it may change slightly with temperature.
So, to stick with the gold analogy:
The amount of gold on Earth doesn't change with time, but the value of gold may.
The amount of salt in the water doesn't change with temperature, but the accuracy of the tool measuring it may.
Also, another part of what Randy was getting at is that the tools we use aren't perfectly accurate to begin with - they always have some range of possible variation.
For example, with the Tropic Marin High Precision Hydrometer (a glass hydrometer that's popular in the hobby), they list their maximum deviation at 77F as 0.001 - so, if your tank water reads 1.026 with the hydrometer at 77F, then the actual specific gravity of the tank (which is technically different that salinity, but most of us in the hobby use the terms interchangeably; sorry Randy) could be as low as 1.025 or as high as 1.027.
The actual amount of variation could potentially change slightly with temperature, though, so to really highlight this variation:
Assuming your hydrometer only reads four digits (i.e. 1.026, rather than 1.0261) and assuming that it has a maximum variation of 0.0011 at 70F (assumed strictly for the sake of showing a variation exaggerated by the temperature difference), then the actual specific gravity of the tank could be 1.0265 and the tool's measurement (rounding to the nearest thousandth/third decimal place, which I personally wouldn't recommend doing with a hydrometer) could show anything from 1.025 to 1.028.
So, you could see quite a bit of variation (even with the actual amount of salt not changing at all) with the same tool even at the 77F, and it could be slightly exaggerated by using the tool at 70F.
As mentioned, though, 1.027 at 70F temp corrected to 77F reads 1.0261 - so even if your hydrometer had that variation of 0.0011, your salinity would still be between 1.025 and 1.0272; both of those numbers would generally be perfectly fine for marine organisms.
So, as long as your temperature-corrected hydrometer reads between 1.025 and 1.027, your salinity should stay in levels acceptable for marine organisms, even with any potential variation of the hydrometer itself.
