Backswimmers (Notonectidae) are common aquatic insects that unfortunately find swimming pools attractive, turning a relaxing environment into a source of discomfort. These pests are predators whose presence signals an underlying issue with pool maintenance, most often an abundance of their preferred prey. Addressing a backswimmer infestation requires a two-pronged approach: immediate removal of the bugs and their food sources, followed by long-term adjustments to prevent their return. Understanding the habits of these insects is the first step toward reclaiming your pool.
Identifying the Pest and Its Bite Risk
Backswimmers are frequently confused with the harmless water boatman (Corixidae). Backswimmers are named for their distinctive habit of swimming on their back, using long, oar-like hind legs for propulsion. They have a characteristic triangular body shape and are often colored with a dark belly and a lighter back. Water boatmen, in contrast, swim right-side up, have a flatter body, and feed primarily on algae.
Backswimmers are predatory insects that hunt small aquatic life, including water boatmen and mosquito larvae. They possess a sharp, piercing mouthpart (rostrum) used to capture prey. When disturbed, a backswimmer may use this rostrum defensively on humans, delivering a painful sensation similar to a bee sting. This potential for a painful bite makes their removal from swimming areas important.
Immediate Physical and Chemical Treatment
The initial step in managing an infestation involves physical removal, which can be accomplished using a fine-mesh leaf skimmer to scoop the bugs from the water surface. Since backswimmers can fly, simply netting them and releasing them nearby may not be effective, as they can quickly return. A more definitive method is to place the captured insects into a bucket containing water mixed with a small amount of dish soap or cooking oil, which breaks the water’s surface tension and causes them to drown.
Backswimmers are attracted to other insects, which are themselves drawn to algae and organic debris in the water. Manually vacuuming the pool is a crucial step to remove sediment and organic matter from the floor. Brushing the pool walls and floor first helps dislodge any clinging algae so it can be filtered or chemically treated.
Chemical intervention focuses on maximizing sanitation to eliminate the bugs’ food chain. Pool shock, or superchlorination, involves raising the free chlorine level significantly to kill algae, bacteria, and microorganisms. For an active infestation, a double or even triple dose of shock is often recommended. Shocking the pool in the evening is most effective, as ultraviolet light from the sun rapidly breaks down chlorine.
Maintaining a consistent free chlorine level, typically between 1 and 3 parts per million (ppm), is standard practice for sanitation. To eradicate an established food source, the chlorine must be boosted to superchlorination levels, often 10 ppm or higher. Ensure the water is circulated for at least eight hours to distribute the treatment fully. After treatment, the water must be tested to confirm the chlorine has dropped back into the safe swimming range before the pool is used again.
Long-Term Prevention Through Pool Maintenance
Preventing algae growth is the most effective long-term strategy for backswimmer prevention. Algae provide food for water boatmen, which in turn become food for backswimmers. Consistent pool maintenance, including regular brushing and vacuuming, removes the organic matter that serves as the foundation for algae blooms.
Maintaining balanced water chemistry is a primary defense against algae and, consequently, backswimmers. Specifically, the pool’s pH should be kept within the ideal range of 7.4 to 7.6, and total alkalinity should be between 80 and 120 ppm. These balanced parameters allow sanitizers like chlorine to work at their maximum efficiency, creating an environment where algae cannot thrive. Regularly testing the water ensures these levels are consistently maintained, especially after heavy use or significant weather events.
Environmental control also plays a role in deterring these flying insects from landing in the pool. Backswimmers and other aquatic bugs are attracted to lights, particularly at night, as they mistake them for bodies of water. Reducing or turning off pool and surrounding area lights during the evening can significantly decrease the number of insects landing on the water surface. Trimming back overgrown vegetation around the pool deck also helps, as it removes potential resting and breeding spots for various insects that could end up in the water.