The sudden appearance of small, swimming insects in a pool is often a sign of an imbalance in the water’s ecosystem. Understanding who these tiny guests are and what drew them is the first step in restoring the pool to its pristine condition. This process involves correctly identifying the species, addressing underlying environmental factors, and implementing targeted removal and prevention strategies.
Common Pool Bugs and How to Identify Them
The most frequent intruders are water boatmen, backswimmers, mosquito larvae, and springtails, each with distinct characteristics. Water boatmen (Corixidae) are brownish, oval-shaped insects, typically less than half an inch long. They are easily identified by their swimming motion, using elongated hind legs like oars to propel themselves right-side-up near the water’s surface. These insects are generally harmless and primarily feed on algae and organic detritus.
Backswimmers, belonging to the family Notonectidae, are often confused with water boatmen but are predators. They are slightly larger, up to 0.6 inches, and have a more streamlined, triangular body shape. Their most distinctive feature is their movement, as they swim upside down on their backs, using long, oar-like legs. Backswimmers are drawn to the pool to feed on other small insects, including the water boatmen.
Unlike the mostly benign water boatmen, backswimmers can inflict a painful “bite” that feels similar to a bee sting if they are handled or feel threatened. This is technically a stab from their sharp mouthpart, which injects a digestive enzyme, causing temporary discomfort. Eliminating their food source, such as water boatmen, is the most effective way to deter them from the pool.
Mosquito larvae, commonly called “wrigglers,” are small, worm-like creatures less than a quarter-inch long. They are a sign of standing water and are usually found hanging just below the surface, using a siphon tube to breathe atmospheric air. When disturbed, they quickly jerk or “wriggle” downward. If left untreated, these larvae quickly mature into adult mosquitoes, which are carriers of disease.
Springtails (Collembola) are minute, wingless insects, typically about 1/16th of an inch long, and are often white, gray, or dark colored. They are not true aquatic insects but are attracted to the moisture on the water’s surface. When disturbed, they use a forked appendage under their abdomen, called a furcula, to spring into the air. These tiny jumpers often accumulate in large numbers on the water’s surface, creating an unsightly film, but they are harmless and do not bite.
Factors That Attract Pests to Swimming Pools
The presence of these insects is a clear indication that the pool environment has inadvertently become a food source or breeding ground. The most significant factor attracting many of these pests is the presence of algae or other organic matter. Water boatmen feed directly on algae, and their presence signals that an algae bloom is beginning. Stagnant or poorly circulated water also creates an appealing habitat for mosquito larvae, which require still water to complete their life cycle.
Unbalanced water chemistry is the underlying cause that allows algae to flourish. If the pH level rises above the ideal range of 7.2 to 7.6, the effectiveness of the chlorine sanitizer is significantly reduced. This reduced sanitizing power allows microorganisms and algae to grow unchecked, creating a food source for water boatmen. Low chlorine levels, often below the recommended 1 to 3 parts per million (PPM), similarly fail to prevent the growth of organic matter.
External factors also contribute to the problem, specifically the use of illumination at night. Many aquatic insects, including water boatmen and backswimmers, are strong fliers and are drawn to artificial light sources. Blue and white lights, which contain high levels of ultraviolet (UV) light, are particularly attractive to nocturnal insects. Furthermore, nearby vegetation, such as overhanging trees, can drop organic debris into the pool, providing both a food source and shelter for pests.
Eliminating and Preventing Pool Infestations
Addressing an infestation requires a two-pronged approach: immediate removal and long-term chemical maintenance. For immediate mechanical removal, a fine-mesh skimmer net should be used to scoop out surface-dwelling insects like water boatmen and springtails. Manually vacuuming the pool is necessary to remove any eggs or organic sediment that the insects may have deposited on the pool floor and walls.
For springtails and other bugs that float on the surface, adding a small amount of liquid dish soap near the skimmer can be effective. This action breaks the water’s surface tension, causing the insects to sink and drown, making them easier to filter or skim out. Once the physical debris is removed, the pool’s water chemistry must be corrected. The water should be shock-treated with a chlorine product, such as calcium hypochlorite, to rapidly increase the free chlorine level and kill algae and bacteria.
Shocking is most effective when performed in the evening, as the chlorine will not be immediately broken down by the sun’s UV rays. Run the filtration system for at least eight consecutive hours after shocking to ensure the chemical is thoroughly distributed. Long-term prevention relies on maintaining the chemical balance and consistent water movement. Keep the pH between 7.4 and 7.6 and the total alkalinity between 80 and 120 PPM to ensure chlorine efficacy. Finally, using a pool cover and switching from bright white lights to warmer, yellow or amber-colored outdoor lighting reduces insect attraction.