Water in a water butt

[froglets]

A drop of washing up liquid will break the surface tension & cause he mossie larvae to drown.  It's dilute enough to not harm anything else.

Cheers

[froglets]

[Phil]

I don't do any of this cleaning stuff and the water always seems OK to me.  Maybe nature is achieving its own balance?   What's wrong with a few mosquitoes anyway, more food for the bats IMO.