I use Mosquito Dunks in all my standing water around the yard, Glen, but not in my pond. The goldfish take care of any mosquito larvae in the pond. So plant pots, puddles, ditches, spots in the rain gutters where the water sits, they all get a little chunk of Dunk about once a month.
The main active ingredient in the Dunks is bacillus Thuringensis subspecies israelensis which is a naturally occurring bacterium that is toxic to the mosquito larvae, but doesn't harm fish or animals. Our cat regularly drinks from the plant saucers and has done for years. She's 13 now, and in pretty good health.
The package does caution you not to use them in water intended for human consumption, but that's just 'covering their you know whats'.
