My tank has been up and running for a week now. Just 40lbs live sand in there with a heater and my emperor 400 filter. The filter has gotten quite loud due to water evaporation. I wanna throw some more water in there. My question is the water i add in do i mix salt in with it or not? Thought i read somewhere that when water evaporates the salt stays in the tank. And if you mix salt in new water your salinity will go up.