As more and more people discover the benefits to having a rainwater barrel harvesting system, they are also learning much more about what mosquitoes like to do. Store bought rain water barrel kits usually come with a cover or screen to seal the barrel opening. Unfortunately, when people build their own barrels from recycled materials they don’t always think to securely seal the top of the rain barrel to keep mosquitos from moving in and settling down. Mosquito control is a vital step if you are serious about harvesting rain water with barrels for future use.
Mosquitoes thrive in water that has been standing still for a long period of time. Wooden or plastic rainwater barrels that do not see much action are an ideal place for mosquitoes to lay eggs or larvae. Mosquitoes will multiply at an amazing rate. So if you see a few mosquitoes taking root in your water barrel don’t just smack them away. A small mosquito problem can quickly become enormous. So how do you prevent or stop a mosquito infestation in your rainbarrels?
Screen or Filter
Start by trying to cover your intake area. A piece of child proof-screen screen is an inexpensive and effective way to keep debris and pests out of your rain water barrels. Believe it or not, even a pair of panty hose could do the trick. Either way you go, make sure that you secure the filter tightly to your barrel opening. Mosquitoes can penetrate the smallest of holes so you will need to check your filter for damage periodically.
Chemical Larvicides or Mosquito Dunks
Mosquito dunks or donuts are made from chemical larvicides. This is a chemical solution that helps eliminate and prevent mosquitoes from making your water barrel their new home. These can be found at your local garden center store and are fairly easy to apply. Dunks are used frequently but there are still those people who shy away from adding chemicals to water that will later be used on their vegetable garden or fruit trees.
Goldfish
Adding a goldfish to your rain barrels is probably the most natural way of getting rid of a mosquito population. This may sound a little crazy but it is very true. Goldfish love to eat mosquitoes as well as their larvae. Goldfish also provide a benefit to the soil in your garden. Goldfish excrement is filled with ammonia which produces nitrogen. Nitrogen is very helpful in plant growth. Remember to leave an opening so your goldfish can get air and food. How else is he to have access to all those mosquitoes? Please keep an eye out for the little guy when you are accessing your water. If he happens to end up in your bucket just gently put him back into the rainwater barrel and let him do his magical work.
* Rain barrel illustration by Annie Bissett, This Old House magazine
Wow, never thought of goldfish as a solution. In most cases a screen should do fine and you really should only have to check it after a big storm. Regular rain showers should not cause a big build up of debris unless your roof is rarely cleaned or maintained.
We found it easier to purchase the rain barrel kit. Of the rain barrel designs out there it was the only one that had a large overflow port that was the same size as the inlet – go figure!