In article ,
Drakanthus writes
The best solution would be to fix the leak, but how you go about finding the
leak I haven't got a clue.

Having said that though, I remember the local water authority used to put
fluroscene die (not sure on the spelling) into water to trace leaks. It is
an
extremely strong die, just a teaspoon full would colour an entire Olympic
sized swimming pool! I don't think it is toxic - but I'd check before using
it anywhere near Koi!

Do check - but it should be OK - AFAIK it's used in caving, to decide
where a disappearing stream resurfaces, and cavers are pretty concerned
about the environment.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/edward/index.htm