"Lee Brouillet" writes:

All right, I'll back off: you CAN buy UV *sterilizers* for water, designed
for household or institutional water supplies. To find one that handles the
kind of flow that ponds have you need to go to a 285 watt UV that will
handle about 3,000 gph and costs $3,688.00. That's HARDLY in the same class
as the 40 watt or less UV's that most ponders use.

Killing all bacteria and killing no bacteria are not the only outcomes. Of
course UV kills bacteria, even sunlight kills bacteria. A pond UV kills
batcteria, but not enough to make unpotable water safe to drink.

"Lee Brouillet" writes:

MOST UV's, and I make that statement with confidence
- do NOT kill bacteria.

Still a false statement.