Protects Against Metal Staining: METALfree is a highly effective metal chelating agent that protects against staining and discoloration from trace metals such as iron and copper. It is recommended to be used as part of a well designed pool maintenance program. Prevents Metal Staining without Adding Phosphate: Metalfree​ does not raise phosphate levels in pool water like many other stain and scale products. Clear Water Protection: METALfree safeguards your pool by preventing both stains and water discoloration, ensuring your pool stays crystal clear. Compatibility: This product can be used with most sanitizing systems and is compatible with all pool surfaces. Note: Do not use with biguanides. Tested and Proven Effective: Natural Chemistry products are known for delivering reliable results and making water care less complex. Natural Chemistry carries an extensive line of pool and spa solutions that match your unique needs. Natural Chemistry 07001 Metal Free 1 Liter Pack of 4