[CoolROD]

I found some more interesting data from this source:
http://www.aquaultraviolet.com/pondbasics.html#7

a single bacterium can produce a colony in excess of 25 million within 24 hours

As bigben2k said earlier -these lamps contain mercury:

Design Importance *5, described the types of UV lamps and how they work. Lamps that produce the greatest amounts of UV radiation contain mercury vapor. There are also high and low pressure lamps. The low pressure hot cathode lamp (T8) is the size of a fluorescent and is used most often in clarifiers as it is less expensive.The hot cathode germicidal lamp is similar in its operation to the standard fluorescent lamp as it operates from a ballast and requires a device such as a glow switch starter to preheat the electrodes located at the ends of the lamp. As the life of the electrodes is shortened by frequent starts, continual use (24 hours a day) is recommended. Hot cathode lamps are made from soft quartz. The major drawback being that solarization and the blackening of the lamp decreases the UV output. The slimline UV lamp is an instant-start lamp available in low, high and very high intensity. This lamp can also be produced in soft quartz and is often misrepresented as hard quartz. *6. Because of their high initial ultraviolet emission and easy maintenance, slimline lamps are well adapted for sterilization and other applications that require high intensity *7. (This lamp is designed to operate at currents ranging from 120 - 420 milliamperes, depending upon the type of ballast. Use of a higher milliampere ballast increases the lamp's UV output. While the lamp may be energized with a lower milliampere ballast, the lamp may only be working at half or even less than its published rating. Therefore it is very important that the ballast is matched to the lamp. Remember, it is not the visible light but the invisible rays that disinfect.

The same number of microwatt-seconds per square centimeter can be accomplished with a short exposure at a high intensity of UV radiation or a long exposure at a low intensity of UV radiation. Our laboratory and field studies have shown a better 'kill rate' at high intensity, allowing us to increase the water flow rate. Low intensity and slow flow rates caused the quartz sleeves to foul converting our sterilizer into a clarifier.

Uh-Oh:

Note that any chemicals containing copper can foul the quartz sleeve, which can alter the effects of the unit. Clean your unit several times to insure all the copper has been filtered out of your pond.

Let's hope that copper will not diffuse into the water too rapidly...any materials people out there?