Your salinity will drop, but how much it drops depends on the volume of your tank and the amount of water you are changing. Why are you mixing the new water at a lower salinity? Just add morre salt to the new water and raise the salinity. Natural seawater around most reefs is 1.026.
Hmmm good point! Well now I am buying reef crystals, I got it to 1.025 to match my tank. 10g has been aerating for the last 72 hours. I did use declorinated tap, new batch will be RO. Had to save for my unit, almost there!
"When you're down by the sea and an eel bites your knee... That's a Moray"