How to fill up evaporation losses?

In my saltwater tank, the water evaporates like crazy. Thus, the salinity level increases. I know you have to top it off with freshwater but I'm afraid that I might make a sudden temp. change or salinity change. I have a starfish, 2 chromis, and a clownfish. The starfish is very sensitive to sudden changes in temp., pH, or salinity. Right now, I'm adding about 350 milliliters of freshwater every day. But, this takes too long, so every once in a while, I have to take everything out, fill up the tank, and acclimate my fish all over again. Thank you soooooooo much!!! :)