Guide to Natural Mosquito Control in Garden Ponds 2022
Spring and summer is often the best time to be a pond owner; as fish are active, plants are blooming, and insects are buzzing – but not all insects are as welcome as others! Mosquitoes love to make ponds their breeding grounds if conditions are right, and this can be a real nuisance if you like to take trips down to the pond frequently. Not only will mozzies give you itchy bites, but they can also cause problems with water quality and clarity if left uncontrolled. Eggs that are laid in ponds will eventually hatch into larvae, but there will still be plenty of waste matter left behind which will build up in your pond over the season. This can contribute to more sludge, smelly odours, and rises in harmful substances, such as ammonia and nitrites.
Although problems with water quality can be a concern, the main reason you likely want to get rid of mosquitoes is to avoid the pesky bites! Sadly, removing adult mosquitoes is very difficult and you’re unlikely to make a significant dent in their population. An adult mosquito’s lifespan is short, however, so the best way to control mosquitoes is to kill the larvae already in your pond waiting to hatch. This is much easier to remove compared to the flying bugs themselves, and there are multiple methods for controlling larvae without the need of chemicals which can be harmful to ponds.
Why are there so many mosquitoes in my pond?
Mosquitoes will arrive every year to some degree, but depending on conditions in your area and around your pond, you could have much less one year and many more the next. Mosquitoes love to breed on stagnant, slow-moving bodies of water and will tend to avoid fast-flowing streams as it’s not ideal for egg-laying. A pond that’s poorly cared for with little aeration will likely have many more problems with mosquitoes in comparison to a highly aerated fish pond.
Maximizing water flow in your pond is the best way to naturally prevent mosquitoes from breeding on your water. Aeration and water movement can be achieved with pumps, waterfalls, and fountains. As well as this, making sure water quality is good and there are no problems with substance imbalance will help prevent mosquitoes from calling your pond their new home.
If you find there are more mosquitoes this year in your pond than normal, it could mean your pond is lacking aeration, water quality is poor, or they’re moving to your pond from a close-by breeding spot (often water buckets left standing).
Are mosquitoes harmful to pond fish and wildlife?
Mosquitoes are actually loved by most garden wildlife, with frogs, fish, bats, and birds feeding off them all season. Just like other insects, mosquitoes and their larvae are good sources of protein, fats, and nutrients and many animals will happily take them off your hands given the opportunity. Problems with mosquitoes are mostly related to us and our tolerance to their bites, but they can also have some negative effects on garden ponds if left unchecked.
For example, mosquitoes can be carriers of bacteria which can make their way into your pond and cause issues with your koi or goldfish. Fish which are already weak due to sickness or injury are particularly vulnerable to bacterial and viral infections, and mosquitoes can further contaminate the water with foreign bacteria.
As well as this, mosquitoes will contribute to waste build-up and can cause issues with water quality as their eggs hatch and decompose in the pond. Although not a major issue for larger ponds, small ponds with low levels of filtration or aeration can suffer under the increased biological waste.
Mosquito Problems in Ponds – What’s the Cause?
Surprisingly, mosquitoes are quite picky about where they lay their eggs, and fish ponds are often not always ideal for these fussy insects to breed. If you have mosquitoes in your pond, it could actually be a sign of an underlying problem, as mosquitoes are known to prefer low-quality water conditions. Some of the more common reasons you may have more mosquitoes than usual are below:
1) Lack of Pond Aeration
Mosquitoes love stagnant bodies of water without much movement on the surface as this is ideal for them to lay their eggs and for larvae to survive. If you have a natural wildlife pond without pumps, water features, or skimmers, mosquitoes have a far greater chance to choose your water as their summer home. Likewise, larger ponds with insufficient aeration can also have issues where some areas of water remain fairly still as they’re further away from sources of water movement.
2) Poor Water Quality
Poor water quality is usually a sign of stagnant water, excess nutrients, or a substance imbalance which may be perfect for larvae to thrive. Making sure water quality is good is a key aspect of safe fish keeping, and often even water that looks healthy could have a growing problem under the surface. Testing water at least twice a year is good practice so you can combat any problems before they can progress and worsen.
3) Unmaintained Pond Equipment
Related to aeration and poor water quality, unmaintained pond equipment, such as pumps and filters, can contribute to a rise in mosquito numbers. Not only will a clogged filter drastically decrease water quality, but it also makes an ideal home for mosquitoes to lay their eggs. Filters without much flow will be a breeding ground for larvae, having all the food and nutrients they need to grow into adult insects. Likewise with pond pumps, if the equipment is clogged there will be less water flow and more possibilities for mosquitoes to begin breeding in the pond.
4) Lack of Natural Predators
A final aspect that can cause an increase in mosquito numbers is a general lack of natural predators keeping them under control. Bats, birds, and frogs are all excellent mosquito killers, but things may have changed in their environment which have caused them to move on. For example, woodland being chopped down, ponds being renovated, or drastic changes in weather could all cause predators to move on to feeding in different areas.
What About Chemical Insecticides/Larvicides?
As with many other chemical treatments, the use of insecticides or larvicides should always be a last resort and should never be used in ponds with fish. Chemicals may be highly effective at killing mosquito larvae, but insecticides cannot recognize “good” and “bad” bugs and will just as readily kill other beneficial insects, such as dragonflies, water striders, water bugs, and damselflies. They are also highly toxic to most aquatic life, including goldfish and koi, as the chemicals easily penetrate tissue and quickly accumulate to poison the fish. Newts, frogs, and all other amphibians are also vulnerable and will quickly die off in ponds where insecticides are added.
So in almost all cases, we strongly do not recommend the use of chemical treatments for mosquito control in ponds. In fact, larvae can even build resistance to certain insecticides over time, which isn’t something seen in natural treatment methods (below). For all these reasons we always urge pond owners to only use natural methods to remove mosquitoes from their ponds, and to stay away from any form of chemical insecticide.
The Best Ways to Control Mosquitoes Naturally in Ponds (No Chemicals)
Method 1: Natural Mosquito Dunks & Bits
- Kills mosquitoes before they're old enough to bite
- The only product with bti, bacteria toxic only to mosquito larvae
- Lasts for 30 days and treats 100 square feet of surface water
This is the best method of mosquito control and larvae killer if you already have a major problem with mosquitoes. Both mosquito dunks (also called “donuts”) and bits work to destroy the larvae that hatch in your water and helps stop them from returning.
The products use a special bacteria strain called Bacillus thuringiensis israelensis – or just “Bti” for short. This bacteria works to kill different forms of insect larvae by producing toxins, of which are particularly effective against mosquitoes, fungus gnats, and blackflies. The bacteria has almost no effect on other organisms or wildlife, and is highly targeted to just kill the larvae of a small range of insects. It’s not toxic to fish, plants, or pets and can be safely used in garden ponds without damage to the eco-system. The other ingredients are all organic and will simply decompose over time when the active substances have been released.
The product comes in two forms, which include mosquito dunks or mosquito bits. The same bacteria strain is used in both, but the method of release is different, being both fast and slow in action. Mosquito dunks are designed to kill larvae over a gradual period, and work great as maintenance doses after treating the pond with mosquito bits. The bits are fast acting and will be able to kill all mosquito larvae in a pond within 24 hours after dosing, so are best used as a treatment kick-start followed by mosquito dunks every month or two.
Unlike chemical larvicides which can cause all sorts of issues for other insects and the eco-system, mosquito dunks and bits will only kill a small range of biting flies and have no negative effects on the pond. Highly recommended for ponds with major mosquito problems or as a control method to stop mosquito larvae from hatching!
Method 2: Improve Aeration and Water Flow
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Although not a direct method of killing mosquitoes or larvae, it’s the best preventive measure to stop them laying eggs in the first place. Mosquitoes will always scout out stagnant water instead of fast moving water, so creating more flow in your pond will help deter them from landing. For smaller ponds, just a pond pump should produce enough water movement, but for larger ponds it may be beneficial to add extra aerators to the system.
Water features, such as fountains and waterfalls, are some of the best natural aerators and also look great in most gardens. For maximum water height and aeration, a regular mains powered fountain pump is a good choice. To save money off your energy bill or for smaller ponds, a solar powered fountain pump is ideal. The water movement produced from extra water features will greatly reduce the chance of mosquitoes laying eggs in the water as it’s no longer safe for the eggs to develop.
As well as improving aeration with water features, air pumps can also be added to provide extra oxygenation and water disruption. Although not as dramatic as a fountain, a strong air pump may be suitable for an area of pond which doesn’t get much natural aeration. The added benefit of this is it provides extra oxygen to the waters, and this is often beneficial to fish in more stagnant areas of water.
Method 3: Add Mosquito Eating Pond Fish
Another fantastic way to control mosquitoes long-term is by introducing pond fish which love to munch mosquito larvae from the water! Fish such as mosquito fish, guppies, rosy reds, or other minnows are all great larvae eaters and should be able to survive in most types of ponds. The fish can even be introduced to combat a mosquito outbreak, as they will breed and multiple in comparison to the amount of food available. They’ll make short work of pretty much all mosquito larvae within a few days, and continue to eat any new larvae which is produced from eggs.
All these kinds of fish are safe to be placed in a pond with both koi and goldfish, and they’re not at risk of being eaten by either. Their numbers will likely grow if mosquitoes are in high number, but they’ll reduce naturally after mosquitoes populations lower. This means they won’t become invasive and cause issues with the eco-system. Their bio-load is also very small, so there should be no significant changes in water quality or problems with filtration.
Although the idea of taking care of more fish can seem daunting just to control mosquitoes, this is probably one of the easiest solutions as the fish are self-sustaining and their numbers are determined by mosquitoes populations so they can’t grow unchecked. They also look great, have quirky personalities, and add lots of life to a pond!
We have a full guide on pond fish that eat mosquito larvae here.
Method 4: Attract Bats to Your Garden
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Another natural predator of mosquitoes, although this time targeting the adult insects! If you have a healthy colony of bats in your garden, you won’t have many flying insects, as the bats will make short work of them every evening when they start hunting. Bats may have a bad reputation as being “creepy”, but they’re actually one of the best natural predators of biting flies, helping to keep populations down so our gardens are more pleasant to walk in.
Sadly, due to over logging and damage to their natural habitats bats are becoming more and more rare across most states. However, there have been recent campaigns by conservation groups around the country to try to reintroduce bats into peoples gardens. The easiest way to do this is with an approved and fully featured bat house which gives them a cosy place to call home. You can also incorporate various flowers that bats are attracted to.
Although it may take a few months, if you invest in the right house and make use of natural attractants, such as bat spray, you’ll likely have some new winged friends in your garden ready for mosquito duty! We recommend the BigBatBox (pictured) as it’s approved by the Organization for Bat Conservation and is much larger than cheaper houses, which means a much higher chance to actually attract some bats.
Method 5: Keep Pond & Equipment in Good Order
Finally, making sure to keep your pond equipment cleaned and in good order will ensure you maintain good aeration and water quality. Cleaning filter media when needed, optimizing filtration, and making sure your pumps are unclogged are all things that can help deter pests and mosquitoes. As well as this, be sure to check out the articles below for further reading on maximizing pond maintenance and water clarity for the healthiest eco-system possible:
I have a new wildlife pond (1 week!), 3m x 2m with lots of shelves for planting which I am still awaiting the plants for. Already mosquitos have moved in with their tiny egg rafts. How can I control them (1 can’t pick them all out) before the wild predators move in? I have a new build house with a walled garden so no easy access for newts, frogs and larger predators.
Good advice about the dunks and bits which I am about to buy. My pond is infestated with the little wormy larvae and happily eating my plants!!
Hi Florence,
We’re so happy that you enjoyed the article! Thanks for reading, and best of luck getting rid of those larvae!
Hi, I just bought a house in northern Maine, there is a pond that is 2 acres in size, the water comes from a natural spring, and is very cold even during summer. What temperature does the water have to be for mosquitos to lay eggs?
Hi Paul,
Mosquitoes are pretty hardy and can tolerate a range of temperatures, and can technically lay eggs in just about any water temperature. However, some studies conducted on various species of mosquito larvae have found that they tend to prefer water temperatures between approximately 18 to 32 degrees C (64-89 F), with the majority of larvae dying in water’s that fall below 16 degrees C (60 F) or rise above 64 degrees C (93 F). If you’d like to check out a short synopsis of one of the studies, here’s the link: https://www.researchgate.net/publication/8518554_Temperature-related_duration_of_aquatic_stages_of_the_Afrotropical_malaria_vector_mosquito_Anopheles_gambiae_in_the_laboratory
In short, if your pond is below 60 degrees F, you’re likely safe from having many mosquitos survive in it! They may still lay eggs, but they’ll be much more likely to either die before even hatching or within a week or so of larvae emerging.