Questions about salt

Hey everybody! I have a couple of random questions about salt...

First, what salt does everybody use? I use Red Reef Coral Pro salt. No particular reason other than it had pretty good reviews. Would people agree or disagree with this salt? If you suggest something different, why?

Second - I have a digital salinity probe from Atlas Scientific. One of the cool thing about this probe is that it measures salinity in both ppt as well as specific gravity, and you can also pass it the temperature of the water so it can make adjustments based on temperature.

However, I am getting a strange reading from it. At 78.76 degrees Fahrenheit, my salinity is reading 34.74ppt. Pretty good, since I am targeting 35ppt based on what I have read online. However, my specific gravity is measuring 1.030.

Those readings are strange to me because using a specific gravity calculator, with those readings my specific gravity should be 1.026, not 1.030.

So I know that .004 isn't very much, and maybe that doesn't matter. But, according to successfulreefkeeping.com, the target for salinity should be 34.0-36.0ppt and the specific gravity should be between 1.021-1.026.

So that means that I am square in the middle of where I want to be for a ppt reading, but I am higher than the "good range" on specific gravity.

So what gives? How can I be great with one way to measure salinity and too high when going off another way? Are there other factors that I am not considering?

The reason I am asking is because I have been battling a terrible cyano outbreak for months. I don't particularly think salinity has anything to do with this, but am trying to rule everything out.