I did a search and came up with a wide variety of old topics on the matter. Most of them don't really answer my question so I'll ask here. I'm having a big problem with mosquito larvae in water all over the property. The only true solution is to dump the water or to add mosquito fish. The problem for me is that my girls are free-range and wander all over the yard. I put water in buckets and bird baths everywhere so they have easy access to water when It's really hot out. I have a bird bath on both the north and south side of the house along with large saucers, buckets, and bowls everywhere. I dump them as often as possible and refresh the water. I scrub them out about once a week. I also have 3 small water gardens. Two are heavy with plants as well as dragonflies and frogs. They're side by side surrounded by all of my sun loving flowers and I've fenced the area off to keep the duck out of the water and destroying my water lillies as well as keeping the chickens from stomping on my flowers. They occasionally get in to drink the water so I'm afraid to treat the water. Question is how do I treat the water. Before I had chickens I would add a chemical that kept the mosquito larva from progressing any further. I can't use that anymore for fear of killing my ladies or causing issues with the eggs. I have used a small splash of bleach on occasion and mixed it quick. It's good to keep string algae away too. What about vegetable oil? It would coat the surface, but at what cost? Is it harmful to chickens? Is it harmful to the plants in the water? Dogs that drink mosquito larvae often end up with heartworms so how can they not be harmful to chickens?