I ended up building this entirely by accident. Last summer I wanted to have aquatic plants in my garden, so I made a small container pond.

As you can imagine it quickly got invaded by mosquito larvae. By the time I realized I was getting raided by mosquitos each night, much more than previous years.

After getting hold of the bacteria (not sure if it's completely allowed here, only Amazon would sell it to me) mosquitos are completely gone, in the pond and around.