Water Change Procedure

I always prepare my water at the same time i did my last water change so the Water is sitting for the week, I have a powerhead and my transfer pump always running in the mixing container. My mixing container definitely has some calcium percipitating out in it. The powerhead is almost white from the calcium.

I have heard if you add magnesium to the mixing tank you wont get all the calcium percipitation. Maybe someone else can confirm this?

I always add my new water into the sump and not the tank and add it slowly through the transfer pumps so I dont shock my tank with the waterchange.

I have definitely seen the cloudiness when adding PH Buffer to the tank but not so much with new saltwater.