Keeping rain barrels mosquito free
I have two different style (commercially made) rain barrels which I
use primarily for watering my vegetable garden. It has become very apparent that the screening on top is not enough to keep mosquitos from breeding.
I did a little searching and goldfish were recommended. I think this would be a dismal existance for a fish and don't even want to think about the water getting low, winter coming, etc.
I do not want to use chemicals since I garden organically.
At this point I have poured several cups of vegetable oil in each with the hope that it will float on top and inhibit the mosquitos. So far it has seemed to be working.
Any thoughts or advice?
I've only heard of fish for this use. I don't believe they have highly developed enough brains to experience a "dismal existence." But then who's asked them?
If you put in fish, wouldn't you need some oxygenating plants? When I had small pond some inexpensive parrot's feather and a few goldfish kept the water free of mosquitoes. The raccoons did eat the fish from time to time. It seems like more trouble than it's worth for a rain barrel.
I think we have the same rain barrel as you do, with the screen. It was my second barrel. After the first season it I never used it again. The first rain barrel I bought 20 years ago is still in use and has no problem with mosquitoes. It's the Great American Rain Barrel, and they recommend draping a Teflon window screen over top of the barrel before screwing on the cover. However, if you have the barrel I think you do, the screen merely sits in a groove on the top. Still, I think an additional screen on top of that one would prevent insects from getting into the water. You could place small rocks around the perimeter of the screen to hold it down. I think you don't want fish in that barrel. It will smell very bad in no time at all.
Here's the GARB site:
You'll want to use Mosquito Dunks. We've been using them for years in our rain barrels (which we use to water our organic gardens). They are made of Bt, a bacteria that will kill mosqito larvae---and harm nothing else! I drop a small piece of these "donuts" in each rain barrel every few weeks or so. You should be able to find them at your local garden center. If not, find them here: http://www.amazon.com/gp/product/B000...
The same company makes it in another form---tiny nuggets sold in a shaker-top cannister. I've used both and they work equally well.