Mixed reef salinity

[Aquattro]

I keep mine at 1.026, simply because an undiluted reef is that value. I don't have any reason to say 1.024 is bad, other than it lowers other values (Ca, alk the big ones) at which point we then artificially raise the levels. I find it hard to believe it's stressful on the fish, as that is what their normal environment is (for reef fish). Local sea water is much lower, but I don't keep local species.
SPS thrive in the wild, at 1.026, and that value matches other things we don't measure (trace elements). Lowering salt lowers other values that may (or may not) be important, so without knowing for sure, I'll err on the side of where the livestock came from. I think, if anything, an unnaturally low level might introduce stress.