I have a 180 gal
reef tank that has been up for a year. Recently I started having salt level drops. The tank will be find for several weeks then have sudden drops in salinity.
I have no leaks.
Salinity drop is not linked to high protein skimmer output.
I use RO
water, and have an automated top off system that does not appear to be adding excessive amounts of RO
water in response to evaporation loss.
I am using a computerized controller and have cleaned the salinity probe and confirmed its reading with a hydrometer. I get the same reading from both.
Since this morning I have added about 10 cups of Reef Crystal salt mix with no change in salinity.
So what could be causing this? I am showing drops on the order of 1.021 to 1.016 over night when this happens.