Why Your Pool Smells Like a Fish Market?

If you’re a fish, then smelling like one is perfectly acceptable. But if your swimming pool has that fishy odor, there’s something wrong, and it’s not something that should (or can) be ignored. There are several reasons for pools having an unpleasant smell, so the first thing to do is find an answer to the question – why does my pool smell of fish?

The fishy smell found in some swimming pools is caused by barium or cadmium in the water or possibly by chloramine, which is a compound of chlorine and ammonia used by local authorities to disinfect the public water supply. Treatment to remove the smell is dependent on its cause and the source.

Unusual smells from your pool, like a fishy odor, may indicate a problem, just like when your pool smells too strongly of chlorine. 

No one enjoys swimming in a pool that has a fishy smell, so finding the root cause is essential in order to work out what treatment will get rid of it. The water may be contaminated before it gets into the pool or may pick up contaminants through poor maintenance. We’ll examine the most likely causes and then discuss how best to solve and avoid recurring problems.

Why Does My Pool Smell Like Fish? Causes and Remedies

The most likely cause of that fishy smell is poor sanitation of the pool, but it might also be that the water used to fill the pool has already been affected by external contaminants.

The External Contaminants In Municipal Water

Some local authorities have introduced a disinfectant into the water supply in the form of chloramine, formed by adding ammonia to chlorine. This purifies the water before it is delivered through the pipes to your home, but an unfortunate side effect is that it might give the water a fishy smell.

Other external causes of the smell could be the leaching of barium into the water from the soil and rocks in the area, which is not unusual. Cadmium is another contaminant, often found in industrial or mining waste, that may find its way into municipal water, also resulting in the fishy smell we are trying to eliminate.

Chlorine and organic material combine to form chloramines that will make your pool smelly, so it’s vital to ensure that you maintain the chemical balance.

Insufficient levels of chlorine combined with body waste, including sweat and urine (yes, folks, you might as well admit it), as well as organic matter like leaves and other forms of vegetation, all play a part in creating chloramines and that fishy odor. It’s not the chlorine that produces the smell but the combination of chlorine and the ammonia contained in the body fluids.

Health Side Effects Of Chloramine In Your Pool

Chloramines can cause skin irritation, burning eyes, and respiratory tract disorders, so it’s not just a question of an unpleasant odor. There are serious health issues resulting from chloramines. It’s imperative to take steps to remove them from your pool as soon as they are detected.

How To Eliminate That Fishy Smell In Your Pool

Whatever the source of the fishy odor in your pool water, the remedies are the same and pretty simple. While chlorine is a factor in causing the smell, it’s also part of the solution. While barium and cadmium are possible contaminants, as I’ve mentioned, by far the most common causes are related to poor pool sanitation.

Increasing the chlorine level will remove the ammonia and thus help prevent chloramine formation. Adding chlorines releases hypochlorous acid and hypochlorite ions, known as “free available chlorine” or FAC, which reacts with contaminants and actively sanitizes the water.

If your pool smells like fish, you may need to adjust the chlorine level, which can also bleach clothes. Learn more about the effects of chlorine on clothes.

Shock treatment, as opposed to regular pool maintenance, involves using a much more potent chlorine concentrate or a non-chlorine sanitizer such as potassium peroxymonosulfate. The effect of this shock treatment can be seen almost immediately as the sanitizer works to reduce chloramine.

Chlorine will kill algae within hours, reduce the ammonia in the water and eliminate the smell of fish. The disadvantage of this type of shock treatment is that you won’t be able to swim for about eight hours, as the super-dosage of chlorine will burn your eyes and skin and even cause breathing issues.

An important point to remember if you own a vinyl-lined pool is to premix your shock treatment rather than sprinkle it directly into the pool – that concentrated chlorine can damage the lining.

Non-chlorine shock treatment, on the other hand, will allow you to get back in the water after twenty minutes. While the sanitizing effect is seen almost immediately, with clear water and that fishy smell under control, a non-chlorine sanitizer doesn’t kill off any algae that may be lurking in your pool, and you will need an additional algaecide.

Supplementary Sanitizers are effective as secondary additions to chlorine in controlling chloramines in your pool, thus eliminating the fishy smell associated with their build-up. These supplementary sanitizers include oxidation, ultraviolet light, and ozone which all work to reduce contaminants in the water without higher levels of chlorine being used.

A fishy smell might be accompanied by other issues like cloudy water. Here's what to do when your pool water is cloudy.

Regular Pool Maintenance Remains The Most Important Task

While shock-treating your pool is recommended and a surefire way to control the growth of chloramines, it doesn’t replace the vital task of regular maintenance of your pool.

  • Using a test kit, check the chemical balance of the water. Adding water will dilute the chemicals, including chlorine, and affect the alkalinity, which means adding pool acid at times.
  • Keep the skimmer box free of leaves and other debris so that the flow through the pump is unimpeded and the water circulates freely. Keep the water level high (covering about one-third of the skimmer box entrance) and ensure the weir gate opens easily.
  • Use an automatic pool cleaner or vacuum regularly to remove dirt and debris from the floor of the pool. Together with the bodily waste we mentioned, these are the primary sources of ammonia and resultant chloramines that give your pool that fishy smell.
Regular pool maintenance can help prevent issues like fishy smells. Keep up with our comprehensive weekly pool maintenance checklist.


Unpleasant-smelling water in your pool can be a problem, but not one that is difficult to solve. The chloramines that build up and cause that fishy smell are easily removed by giving the pool the shock treatment I’ve discussed and not forgetting to follow a regular maintenance routine to ensure that the chemical balance is maintained. Do that, and your pool will be a sweet-smelling pleasure to use!