Alla Bezroutchko wrote:
Is there any way to prevent mosquitoes from breeding / laying eggs /
whatever it is that they do in my rainwater butt? There seems to be a
lot of them in there, at least when the butt is partly empty.

I don't want to increase the mosquito population, particularly close to
the house where I live.

Alla.
a cheap goldfish from your local garden cent it will thrive on the
larvae - no need to feed.