We stock premium High Output Ultra Violet pond Clarifiers & Sterilizers as well as replacement parts. To help you understand the difference between Clarification & Sterilization here is a Rule of Thumb to help guide you. To Clarify we recommend 10 watts of UV per 1000 gallons of pond water and for Sterilization we recommend 30 watts of UV per 1000 gallons. Use higher intensity and slower water flow for pond sterilization. When using UV to clear green water problems, 10 watts per 1000 gallons of pond water is typically adequate. Pond UV Clarifiers are great for Koi Ponds, Water Gardens & Hybrid Ponds.