The K+ ions of potassium compounds have some selective activity, being highly toxic to zebra mussels, where they interfere with membrane integrity and respiration (Fisher et al. 1991; Claudi and Mackie 1994), but not affecting fish (Waller et al. 1993). While too harmful to native mussels to have gained approval for use in once-through systems, potassium is suitable for contained or closed-loop systems, or those such as fire protection systems where outfall of large amounts of concentrated solutions is not a problem (Claudi and Mackie 1994; Lewis et al. 1996). A method for treating such semistatic systems with the effects of potassium ions (K+), using commercially available potash has been developed by Aquatic Sciences, Inc., Canada. As an unregulated, low-cost product, potash has been shown to be acutely toxic to mussels under both warmwater and coldwater conditions (>5 ºC). At relatively low levels, potassium also appears to be a selective molluscicide. Since potash is regularly used as a fertilizer in agriculture, it is widely available and generally regarded as safe.
Chemical Name and Commercial Formulations
Timing and Appearance of Effects
Field Instructions and Guidance on Operational Applications