Alum is a loosely defined chemical group, with different formulations depending on source and differing weight of Aluminum for a given weight of the alum. So does it really matter which you use? Most floc treatment recipes are trying to remove excess Phosphorus and talk about the amount of aluminum required per ppm of Phosphorus, but usually don’t specify which “formula” for Alum they are using. Are some types easier/safer to use? Are some more easily dissolved/slurried? Cheaper per weight of Aluminum?