Applied biochemists thio trine reduces or eliminates excessive chlorine or bromine levels. This product contains special 100% sodium thiosulfate crystals neutralize residual chlorine or bromine in pool and/or spa water. This product works quickly & effectively so you can prevent pool downtime due to excessive chlorine or bromine levels. In addition to working in chlorine or bromine systems, this product also works with pools sanitized with biguanide. Reduce sanitizer to safer, more comfortable levels with thio trine.