Methods of treating water to promote the health of aquatic organisms are described. The method may include introducing pulverized kaolin into the water. The pulverized kaolin may have a particle size distribution such that at least 30% by weight of the particles pass through a 60 mesh screen. For example, the pulverized kaolin may be in the form of a dry powder having a d50 diameter less than 300 µm. The pulverized kaolin may remain dispersed or suspended in the water without dispersants and/or surfactants, e.g., to reduce the amount of at least one pathogenic microorganism present in the water and/or to reduce or prevent exposure of aquatic organisms to the pathogenic microorganism(s).
