My top off container is filled with fresh RO
water (never had salt in there). I understand why it dropped to .021 but I had to get my tank level back up for the skimmer and hang on fuge. I've unplugged my ATO and mixed up 5 gallons of new salt water which I plan on slowly using to bring sg
back up until this weekend when I can do a larger water change.
I have completely wiped down the tank and will be looking for any signs of salt creep over the next week or so while I'm going to be local. I also ordered glass tops to minimize evap when I travel for longer periods of time in the future.
I swear if I didn't know better I would say someone came in and borrowed 15 gallons of water from the tank.
I've been doing reef tanks for over 3 years now (with most of the same equipment) so while I'm not ruling out a possible "jack daniels" moment during my last measurement I'm still stumped.