The most reliable way to remove harmful bacteria in fresh and seawater aquariums. With the hw UV water steriliser, only the water flowing past the UV steriliser is irradiated. In this way, only harmful microorganisms (germs, organisms causing water turbidity and suspended algae) are destroyed. The nitrification bacteria essential for the biological balance in all aquariums, which adhere to the aquarium filter, bottom of the aquarium, plants and stones are not harmed in any way. Hw UV water sterilisers are provided with a special glass UV protective jacket, which effectively blocks the radiated UV light, but allows the unharmful, visible light to pass through. This reliably protects animals and humans from direct UV irradiation. There is also no danger to the human eye, even when looking directly into the light.hw-UV-water-sterilizer for seawater aquariums:- Standard method to optimize water quality and care conditions- Effectively prevents bacterial tissue damage of sensitive corals- C