Bti

http://www.who.int/water_sanitation_health/gdwqrevision/RevisedFourthEditionBacillusthuringiensis_Bti_July272009_2.pdf

Interesting review of Bti.

I continue to use it in the garden pool, not sure how beneficial it is because there are so many other factors to consider.

For example, the bats I see darting overhead at dusk might have a significant effect on mosquito populations.