Good tip, spyder813.Oh wow. An ATO is very important on a reef tank cuz it keep the salinity stable. Maybe you know that the water evaporates but not the salt so the salinity will go up and that can kill all the livestock on your fish tank. I did a top of manually at the beginning but once I did my gravity ATO my system became more stable.
Unfortunately, as my tank is set up right now, a gravity ATO is not an option. I only top off with RO/DI, not salt water and my levels only vary in 0.5 ppt. I will definitely look more into an ATO solution or top off daily to keep the salinity constant. When the time comes to upgrade, I will definitely plan for an ATO.