A novel method and compositions are disclosed for the treatment of water in recirculating water systems. The method includes providing a boron level of at least 20 ppm in the water, continually eroding into the water a compressed sanitizer/algicide component including a halogen source material, a boron source material, and glycoluril, and periodically adding to the water an oxidizing clarifier comprising a chlorine source material, a non-halogen, chlorine source material, and a boron source material. The invention also provides novel water treatment chemicals including the compressed sanitizer/algicide component and the clarifier useful in the foregoing system. The system and compositions are safe and reliable, control algal and fungal growth and generally provide improved water quality for recirculating water systems.