Keeping a Water Feature, Without the Mosquitoes!

A water feature can be a positive addition to your garden landscape. It will create a relaxing feel and an interesting focal point and is also said to be good Feng Shui, especially if the water is flowing. The main downside to keeping a water feature is that it can easily become a breeding ground for mosquitoes, which are not only annoying but potentially dangerous. They can transmit diseases such as malaria, dengue fever, and encephalitis, or even heartworm to your beloved pets. For this reason alone home gardeners often feel reluctant to add any water source to the landscape or home. Don’t let those pesky pests put you off! For every problem there is always a solution! With a few easy precautions you can have a water feature and still feel safe that you are not providing a breeding ground for mosquitoes.

There are a number of ways that you can prevent or reduce mosquito production. The simplest, laziest, and easiest way is to add BTI larvacide to the water. BTI is a naturally occurring type of bacillus bacteria that is eaten by the mosquito larvae, and rapidly kills them. It comes in tablet form and you simply drop into the water. It is not harmful to fish, pets, wildlife or humans, so you won’t have to worry if your dog or cat drinks the water. It is usually sold under names such as mosquito dunks or mosquito bits, and is readily available at good hardware stores and from the internet. It is also relatively cheap. If you don’t have aquatic plants or fish, and you need a one off solution to control a heavy infestation, a simple home remedy is to pour vegetable oil directly onto the water. The oil works by putting a film over the top layer of water, which prevents the larvae from breathing and penetrating the surface. If you have fish or aquatic plants within your water feature obviously this is not a suitable remedy.

The next easiest solution is to add a submersible pump, a waterfall or fountain. Flowing water is pleasant and will also enhance the water quality. If it is possible keep the water flowing at all times. Mosquito larvae can only survive in stagnant water. Newly hatched mosquitoes must rest on the surface for a few minutes to let their wings dry, because of this they will not lay eggs in water that is constantly moving.

If you can only run your pump for a few hours a week then the next best option is to incorporate mosquito eating fish into your water feature. Many varieties of fish prey on mosquitoes. They won’t stop mosquitoes laying eggs, but they will eat the larvae and prevent them from growing into adults. Goldfish, white cloud minnows, zebra danios and the betta fish (also known as the Siamese fighting fish) are all excellent choices for controlling mosquito outbreaks in your pond. Koi on the other hand are too large and will not target the larvae. The white clouds or the black and white stripy zebra danios are my personal favorites for a pond as they swim in a school, are attractive and easily munch up all the larvae. I once had an old aquarium out the back that had filled with rain water and hundreds of mosquito larvae.

I added as little as ten minnows and watched in amazement as they hunted down and devoured every last one. Within half an hour they had eaten every single mosquito larvae, not a single one left. And then after that, they kept on hunting for the next half an hour just to make sure that there were no more! I personally guarantee that these fish love to eat mosquito larvae. Minnows are very small, hardy and will companion well with goldfish, or Siamese fighting fish who are both also known for their ability to control mosquito numbers. It is important to note that the Siamese fighting fish is named so because of its behavior towards other males of the same species. You cannot keep two or more males in the same pond as they will fight each other until only one remains.

Proper maintenance will also contribute to reducing the mosquito danger. Water trapped in the top of pots, shallow margins, water trapped between rocks, thick aquatic plants all provide protection from natural predators (fish and insects). By managing these areas you will minimize opportunities for mosquitoes to hatch in your pond. If you have submerged pots in your feature, make sure that the edge of the pot is below the water’s surface. Fill in any small pools of water between larger rocks with gravel. Thin out any dense growths of aquatic plants, or overgrown plants around the water feature. Dense or overcrowded aquatic plants provide safety for mosquito larvae. Thinning them out allows the fish and water to circulate easier. Remove any excess organic material from your pond such as leaves or grass. This material provides food for mosquito larvae and can also shelter them from natural predators.

For mosquito prevention, your best option is to cover all bases and use a combination of all of these strategies. Run your pump for a few hours, add some fish, and regularly maintain overgrown or trapped water areas. Ideally a pump running for at least a few hours per day combined with suitable mosquito eating fish is the ideal set up for a home water feature. I would recommend adding ten minnows or zebra danios in conjunction with two or three goldfish, and maybe even a Siamese fighting fish. Make sure not to over feed the fish as they may not eat the mosquito larvae if they are not hungry. If you aren’t able to add fish then add some BTI or mosquito dunks. The way I see it, mosquitoes are essentially the weeds of the water garden, and just like real weeds with regular maintenance you can easily de-weed your water feature of those nasty mosquitoes.

Dr. Kris
Garden Doctor
Copyright © 2011 Dr. Kris
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