Nicknamed a "snowstorm". It is when Ca precipitates out of the solution and it makes the water milky white.
If I may add:
water (especially) saltwater can only hold in suspension a maximum number of particles at a given temperature... due to the velosity of the molecules which are directly coorelated and directly proportional....
therefore, at a given temp. the water can hold upto its saturation level of things like salt, Ca,.....
If the temp was to drop while the water was at saturation level, or an attemp to add more when the water is at saturation level- the waters inability to keep the solution suspended will likely result in what is called precipitation ( the excess falling out of the water in its original form)
Also I agree with placing the brain in the sand- for if a coral has mantle extension beyond the tob of its coral stucture: ie brains, plates, tounges...etc. It is risky to blace them on rock where it is likely to have its mantle riped which opens room for infection...
Strontium and Molybdenum are also useful to the coral in its quest to repair the flesh...