A refreshing dip in the pool can be cut short by the sudden appearance of uninvited guests, especially if those guests are a bunch of squirmy red worms. These --- and other surprises --- can appear from one day to the next and leave you puzzled and wondering what they are and what to do. In the case of tiny red worms, there are likely to be only two candidates, and both of them can be dealt with fairly easily.
Tiny red worms swimming freely in your pool water are most likely to be bloodworms. These little bugs are actually midge fly larvae, and only occur if the conditions are right for them. They live in clean water that is clear, not muddy or full of other debris. They also do not live in moving water, such as streams and rivers, but thrive in the still waters of ponds and lakes and, sometimes, swimming pools. The eggs are laid by adult flies in areas that are likely to support the young.
Worms at the Bottom
Small red worms found living on the bottom of a swimming pool are probably tubifex worms. These worms live only in muddy, dirty environments, so if the pool has an accumulation of debris on the bottom, and especially if there is mud there, it could be hosting a colony of these worms. Tubifex do not swim freely in the water, but instead live in clusters on the bottom. They prefer slow-moving water but can sometimes be found in ponds and other still water. Tubifex eggs can be introduced into a pool by contamination due to bird droppings, via a frog or other animal getting into the pool or mixed in with mud that gets into the pool.
If either of these types of worms is found in the water of an above-ground pool, it is a signal that the water quality is poor. Although bloodworms live only in clean water, if the pool is properly chlorinated or otherwise has had the water sanitised, the worms cannot survive. The presence of tubifex worms indicates a serious problem with the water, since these worms live only in dirty, muddy places.
To get rid of either type of these tiny red worms, it is necessary to create conditions in the pool that will not allow them to live there. Skim out as many worms, leaves, mud and other debris as possible. Treat the water with chlorine according to the label directions. Run the filtration system to mix the chlorine into the water and to filter out any remaining worms. If the pool is to be left unused for any period of time, keep it covered so that no pests can get in.