aquatrades is a interesting website, Id just be careful when dealing with them.
"Ultraviolet Sterilization is a proven, dependable, and effective method for controlling and eradicating algae spores, bacteria, and protozoa (i.e.: ich) present in the water column. It is extremely beneficial in destroying disease-causing pathogens as water is pumped through the unit. Some sterilizers can be used in both saltwater and freshwater (aquariums or ponds).
For the treatment of disease in an aquarium, an 8-9 watt UV sterilizer will handle a tank up to 50 gallons, a 15W UV sterilizer will handle a tank up to 75 gallons, a 25W will handle up to 120 gallons and a 40W will handle up to 180 gallons. For tanks larger than 180 gallons, please contact us for sizing details. For pond applications, 8 watts per 1000 gallons is needed to kill off algae (green water).
Sterilization and purification of water by the use of ozone has been used for many years in drinking water and wastewater treatment plants throughout the world. Ozone is a very reactive form of oxygen that can destroy an enormous variety of liquid waste materials and toxins. In the aquarium, it offers a simple, highly effective method of maintaining a clean and stable environment for the plants and animals. As a rule of thumb, we recommend 1 mg/hr for every 2 gallons of aquarium water."
-Marine Depot Definition