I also just recently found out what mosquito dunks are. https://summitchemical.com/products/mosquito-dunks/
And they are simply BT toxin –not good for pond wildlife. They poison the base of the food chain and are toxic to dragonfly larvae, diving beetles, tadpoles, damselfly larvae and all the little cyprids and fun stuff in your pond. Likewise mosquito fish are incredibly bad for ponds. They are not native in California although in some of the southern states they are, but they will eat the little native frog tadpoles preferentially to mosquito larvae.
Certain common species of Dragonflies when they are laying eggs dip their tails into the water and flick water droplets so that it is hard for fish to see which water droplet the egg is in. But mosquito fish swarm them. I have a general policy not to work on ponds that have mosquito fish in them. Goldfish are bottom feeders and much more likely to miss quite a few of the scattered eggs.
Even in a small pond there are little solar pumps that you can put in that work well in keeping mosquitoes out. Mosquitoes do not like agitation of the water surface. You don’t need to have it actually be a fountain as long as it is stirring the top of the water. Enjoy your water feature!
Oh I just saw a post on X and now I’m annoyed. The post said that BT toxin will not kill dragonflies. Technically, in a twisted, word manipulation, way this _might be_ true. However while it _may_ not kill adult dragonflies (would love to see some long-term data by the pesticide industry since they make this claim in the first place. Like so many who say it can’t hurt something but don’t provide any data) the manufacturer of this product knows perfectly well that it will kill dragonfly larvae.
The general idea behind the term “lying by omission” is if the _intent_ is to deceive …. There is no doubt in my mind that their intent is to deceive you. Mosquito dunks will kill dragonfly larvae, damselfly larvae, and water beetle larvae. It is also particularly not helpful to Tadpoles, and bees.
Search this site for bees and you will find me discussing how they cool their hives by evaporative cooling. BT toxin in this water will dry on, and in their hive. This is not good for them. It may not be enough to destroy the hive but if the hive is being slowly poisoned….
Pesticide manufacturers are very careful with the words that they choose to use to mislead you.