adjusting current tank salinity levels

I have a new tank up and running for about a wek now. Some sand and live rock. Originally newly filled tank measured good, but last couple of days it has measured a little low on salinity. I had been adding 1/2 gallon per day to my sump due to evaporation and that was not mixed salt water. What is the best way to mix in to bring levels back within range? I started to add back to my sump today with mixed saltwater hoping this would help. Any thoughts?

 

You've got the right idea. Keep topping off with saltwater until you have your salinity where you want it. Just use saltwater around 1.025 SG for your top off.