Tips and advice

Preventing boatmen bugs and water beetles in swimming pools

December 7, 2017

Following recent reports of a resurgence of small brown bugs in swimming pools, we are reprising this article on water beetles.

These bugs are commonly called water beetles, but are more accurately known as Cybister tripunctatus and are a part of the Dytiscidae family. They are similar to “boatmen” and have been found in large numbers in Queensland swimming pools from the Gold Coast to the Sunshine Coast.

These insects prefer habitats of slow-moving or stagnant water. Usually confined to the Murray-Darling basin, they fly about at night looking for the reflection of water to establish a new habitat.

A cause of these beetles breeding in large numbers is unusual wet weather conditions, leading to these insects being able to breed and easily move from one habitat to another, using the excess water as “stepping stones”. Although they are not dangerous, they do have small pincers and can bite.

Currently, there is no complete and effective way to prevent these bugs from getting into the pool, but there are steps that can be taken to try to limit their numbers as well as treatment once they are in the pool water.

BioGuard Education Officer Bill Mansfield has put together some information to help control the beetles.

Pool covers: Water beetles fly at night and look for the reflection of water to land in. If the owner uses the pool cover at night, this will greatly reduce the reflection of the pool surface – resulting in far fewer beetles in the pool.

Outside light: These insects are also attracted to light, so by turning off the outdoor lights around the pool area, it should also reduce the number of beetles that end up in the pool.

Water beetles require air to survive. They go to the surface to gather air, which they store under their wing covers. As such, the best treatment to eradicate these bugs from your pool is to use a quat-based swimming pool algaecide or surfactant that contains non-ionic ethoxylate. These break the surface tension of the water, while preventing algae growth from the dead insects, and will stop insects from holding onto air while swimming. Hence, the insects will drown and drop to the bottom where the pool vacuum can remove them.

This will remove the insects from your water but until they stop breeding and spreading, this will only be a treatment to remove them after arrival. Prevention is always better than cure.



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