This replacement bulb is designed for use in TetraPond GreenFree UV Clarifier for ponds. This high-efficiency bulb has an 8 000-hour life so it should be replaced after 11 months of continuous operation. Make sure to replace every pond season – the bulb may continue to glow but its effectiveness in killing algae diminishes. Convenient viewing window in TetraPond GreenFree UV Clarifier makes it easy to ensure the bulb is working. This bulb is 35 watts for ponds up to 8 800 gallons.TetraPond GreenFree UV Clarifier (not included) works to keep your pond clean clear and free of unsightly green algae. These dependable clarifiers use ultraviolet light to destroy suspended green algae. As algae are pumped into the clarifier they are exposed to ultraviolet light that destroys the reproductive ability of single-celled algae. The dead algae are then pumped out of the TetraPond GreenFree UV Clarifier where they clump and are removed by your pond s filtration system. Removes heavy algae blooms (usually within 8 days) and keeps the pond algae-free long-term.Since 1951 Tetra has developed the world’s most comprehensive body of fish food knowledge and fishkeeping enthusiasts have looked to the brand for products and solutions that add ease and beauty to their home. Whether you re an experienced hobbyist or just starting out Tetra has everything you need – from a large variety of quality fish food and innovative equipment to test kits and decor.