Will my ornamental ponds increase my mosquito problems?
Ornamental pools and landscape fish ponds can be potential mosquito breeding sites, but they don't have to be. Here are some things to consider:
• Check the pond regularly for mosquito larvae and pupae.
Kneel down by the edge and watch the water carefully for the distinctive wriggling mosquito larvae and tumbling mosquito pupae. They must come to the surface regularly to breathe, so just get comfortable and watch for a while. They are most likely to be found in warm, shallow areas of the pool. Weekly checks will help you to know whether mosquitoes are thriving and whether you need to implement control measures.
• Stock your pond with goldfish or koi:
Healthy and hungry top-feeding fish can help to control mosquito larvae and pupae. Smaller goldfish or koi, if hungry enough, will generally eat mosquito larvae and pupae. If you notice wriggling mosquito larvae, stop feeding your fish for a few days and see if the larvae disappear. Do not overfeed your fish. Hungry fish make better mosquito predators, and you will not have leftover food to encourage algae growth.
• Keep landscape plants trimmed away from pond edge:
Ground cover plants or other landscaping plants that touch the surface of the water can provide a base for algae growth and shelter for mosquito larva. Keep surrounding plants trimmed away from the water surface so this will not be a problem.
• Remove excess organic material from pond:
Remove dropped leaves and other organic matter that fall into the water. Excessive organic matter can require more oxygen than the pond has available for decomposition. The anaerobic (without oxygen) bacteria that grow in this situation discolor the water and give it a foul odor. Most mosquito larvae do well in stagnant water because they feed on the microorganisms.
A mosquito control product that you might consider is Mosquito Dunks. This product contains a biological insecticide and can be placed in ponds to control mosquito larvae. It does not affect eggs or pupae but will kill larvae. The product does not provide fast results and is most effective against small larvae. It is safe to use with fish and other aquatic animals and will not harm plants.