The mosquitoes obviously are not breeding in the water you give the girls, so the first thing to do is determine where they are coming from. Once you find the source, you can do start to do something about it.
Mosquitoes and I have a love hate relationship. I hate them, they love me. I cleaned out a previous neighbor's pond several times a year for 18 years in order to be mosquito free. Could have reported them to the County, but we like our neighbors more than that.
I see jomoncon recommended dunks. I have had mixed results with dunks. Initial success, but ultimately, I can't say I was impressed. My long standing favorite is ten for a dollar gold fish. I keep fish in all my water sources regardless of size. Rain barrells, ponds, even nooks in trees. There's a tree in the woods that holds about five gallons of rain water. For years I've fished out the season's debris and flushed it out, but this year I figured it was time to try fish. I've got them everywhere else, why not there? Of course, a simpler solution would be to just drill a hole at the base of the catch basin so it doesn't fill up in the first place. Alas, I don't have a power drill and all my hand drills are too weak for it. It's been on my to do list for 25 years. Just haven't gotten there yet.
Netting is also a good way to get rid of mosquito larvae. Just swipe a fish net through the water and dump them on the ground.
Anyway, let me know where and what is the water source that is allowing mosquitoes to breed and I can be of more help. Otherwise, and it's a good idea either way, your best bet is to contact your local County Vector control office.
Best of Luck!
PS Frogs. I'm also really big on frogs. You have to start them out as tad poles, but once they get to be frogs, their gobble up everything!
