I've noticed after salt mix is prepared in buckets to the perfect salt concentration then added to the aquarium the specific gravity in the aquarium drops by as much as 0.002 OR FROM 1.024 to 1.022 and then I have to quickly mix a cup of salt in a small amount of warm water and begin fine tuning.. getting good at it... I use 75 degree RO water and the aquarium is also 75 degrees. I allow the mixed buckets to sit about 5 minutes. I use a refractometer. My salt mix is the manmade stuff with all the minerals for reefs. Is this normal? Is this unsafe?