On 2006-10-08 10:12:47 +0100, said:


How can one safely tell if a UV lamp is working? This is a UV tube in
a pond filter system which lives in a lightproof (well, UV proof I
suppose) tube with the water going to the filter flowing past it.

It has standard fluorescent gear, a choke and a starter.

That's a tough one.

I have something similar used as a steriliser for a reef tank.

The problem is that they don't suddenly stop working, but rather the
output degrades.

Generally, therefore, one replaces them according to time - mine is
changed every 6 months.

For a pond system where the UV is usually used to control algae, one
could look on the basis of whether the algae is being controlled.
However, as you probably know, algal growth depends on sunlight,
temperature, nutrient availability and your inside leg measurement, so
it is not always easy to make an assessment of whether the UV treatment
is doing its job.