Aqua Ultraviolet is the industry leader in ultraviolet sterilization for ponds. Aqua Ultraviolet UV bulbs last an industry high of 14 months (versus 3-6 months of other brands) and deliver a 99.9% effective kill rate. Bulbs are easily changed by a one-end, four pin connection, eliminating the need to dismantle the unit for bulb replacement. Bulbs are protected by a HL Q200 quartz sleeve, which allows the bulb to reach its optimum operating temperature while allowing 99.9% UV transmission for higher flow rates. Ballasts are self-starting, thermally protected and designed for outdoor use. All UV housings are weather-resistant, UV-resistant and feature a limited lifetime warranty. Aqua Ultraviolet units are UL listed and are the only UV sterilizers on the market that feature EPA approval. When it comes to ultraviolet sterilization, there is no other choice. Easy twist-off cap for easy cleaning of quartz sleeve!