Omg! All summer long I had issues with my magnesium dropping after water changes. This must be why! This caused huge problems in my tank because my calcium and mag was in one solution. I have since switched over to fauna Marin balling salts and do a 3 part dose!Myself and my LFS have been having a problem with reef crystals mag being low. Fresh batch at 1.026 was testing 1200 for my box and my lfs.
Contacted spectrum brands and they are making it right. I also sent them a sample of the water and a sample of the salt I was having a problem with.