First and foremost...Welcome to the R2R community, if in fact you are new. If not...glad you came back!!
Agree that the slurry is not necessarily bad...the issue at hand is that it is caustic. With saturated Kalk you kind of have a known commodity and a general understanding of how much Kalk is entering your water column. with the Slurry, could be 1x, 5x, 100x who knows. Just harder to control the variables when you are dumping and unknown amount of kalk into the ecosystem.