Can Cats Drink Aquarium Water? (Risks, Facts, & Precautions)

Cats are obsessed with fish aquariums. Just like us, cats also love watching the fish swim by.

However, unlike us, cats are often jumpy, hyper, and curious in nature.

If you have an aquarium in your home, there is a 99% chance that your cat has tried attacking it at least once.

The funny thing is that cats don’t attack the fish in the aquarium; in fact, they are more obsessed with drinking water from it.

Cats love the fish water, even if it is dirty. In fact, they prefer aquarium water over clean water in their bowls.

Guess we can never know what goes on in their heads.

But the question is, can cats drink water from your fish tank?

Can Cats Drink Aquarium Water?

No, cats should not drink aquarium water.

People who keep fish tanks and cats in their homes are aware of how cats just love to knock off the aquarium lid and enjoy the water that has the scent of fish.

While this is a very common phenomenon, it is NOT okay for cats to drink aquarium water as it can lead to a number of problems.

Cats do really enjoy drinking water from an aquarium when they are thirsty, so much so that they will not drink clean water from their own bowls.

Many people believe that this is because cats are intrigued by the bubbles in the fish tank, or they like the smell of fish along with their water.

Many cat owners have reported that their cats do drink water from the aquarium, but they don’t discourage such behavior.

Since cats can’t be caged, they can easily find their way to the fish tank and drink water from it.

Not many people have reported how serious this issue can be and how it can lead to many problems.

Reasons Cats Should Not Drink from a Fish Aquarium

Here are some reasons why cats should not drink aquarium water.

Fish Tank Water Contains Toxins

Aquarium water has tons of toxins and bacteria that aren’t good for your cat.

Maintaining a fish tank is not an easy task, especially if you have a number of fish and corals inside it.

The quality of water changes every now and then.

If a cat drinks water that contains these toxins, it can get sick.


Aquariums have a nitrogen cycle that determines how the fish waster is processed.

The fish waste is released in the form of ammonia, which is highly toxic for all living organisms.

When the ammonia released in the water combines with the bacteria living in the aquarium filter, gravel bed, and other objects, it forms nitrite (NO2), which is equally toxic.

This nitrite again reacts with other bacteria and converts to nitrate (NO3).

Nitrate is not harmful to aquatic organisms, but it is harmful to humans and animals. Cats can suffer from nitrate poisoning if they are exposed to it for a time period.

Even though such cases are seldom reported, nitrate poisoning is highly dangerous and can lead to death.

If cats consume water that contains nitrates, they can suffer from gastrointestinal and cardiovascular, problems. Signs of toxicity start showing after the second or third exposure.

When cats drink water directly from the fish tank, they are swallowing the nitrates that can severely affect their health.

The Water has Fluctuating pH Level and Hardness

Fish tank water is not only considerably dirty, but it also has a fluctuating pH level and general hardness, making it unsuitable for your cat.

pH Level

Aquarium water generally has a fluctuating pH level as its biological and chemical properties keep on changing.

If the pH level of the water is higher than 8.5, it is considered to be alkaline, which is not safe for humans or animals.

If the pH level of the water is below 6.0, it is considered to be acidic, which is also not safe.

The pH level of an aquarium is usually low due to the breakdown of organic material. This means that aquarium water is mostly acidic.

This water is, hence, bad for your cat as acidic water causes a number of issues, including vomiting, diarrhea, kidney or liver disease, and stomach cramps.

General Hardness

Water hardness determines the amount of calcium, magnesium, and other ions present in the water.

Aquarium water generally tends to be hard as it contains aquatic species and plants and is exposed to a number of biological and chemical changes over time.

If your cat is exposed to unfiltered hard water, it may cause health issues.

Carbonates and Bicarbonates

Aquarium water also contains high levels of carbonates and bicarbonates until it is cleaned up.

In the meantime, if your cat drinks that water, it can cause digestive and respiratory issues.

Carbonates and bicarbonates are not a serious health hazards, but they may slowly cause problems for the cat.

Uneaten Fish Food is Dangerous

Aquariums commonly have huge amounts of uneaten fish food, which contaminates the water with ammonia and nitrite.

The uneaten fish food makes the water dangerous for any human or animal that is exposed to it.

If cats drink that water, they can develop serious health issues as ammonia, phosphate, and nitrite aren’t good for their bodies.

Furthermore, uneaten fish food releases toxic ammonia and phosphate, which eventually leads to algae growth.

The decomposition process of the fish food uses oxygen present in the water tank, thus reducing the amount of overall oxygen in the tank.

The process also releases carbon dioxide, making the water carbonated.

Since uneaten fish food particles clog the filter, the circulation in the aquarium is limited, and thus more bacteria are collected.

We can only imagine how toxic all this can be for our cat that drinks the contaminated fish tank water.

Cats can suffer from kidney, liver, internal organ, and respiratory tract problems if they drink such contaminated water.

To prevent this from happening, you can keep your fish tank clean of all bacteria and maintain the aquarium water quality to protect all fishes.

Moreover, you can also try to keep your cat away from the fish tank.

Exposure May Cause Skin Rashes

As discussed above, fish tank water contains bacteria, ammonia, nitrate, and other chemicals.

These chemicals may not be as harmful to the fish as they are to humans and animals.

When cats try to drink aquarium water, their face comes into contact with the water.

The algae growth, ammonia, and water hardness levels may cause skin irritation and rashes.

Since cats are already vulnerable to a number of skin diseases due to the bacteria present in their fur, exposure to toxic water can increase the chances of skin rashes.

Furthermore, when a cat climbs on top of the aquarium and tries to drink water right out of it, it may drop some fur inside the tank, which can be dangerous for the fish.

Cat Diseases Are Hard to Diagnose

Another reason why cats shouldn’t drink aquarium water is that cat diseases are hard to diagnose.

This means that even if your cat is suffering from a problem or has some sort of bacteria growing, it’s almost impossible to tell until it gets worse.

The levels of toxins in a cat’s body are hard to investigate and diagnose, even by a vet.

How to Keep Cats Away from the Aquarium

If your cat refuses to stay away from your tank or aquarium, you need to take some measures so that your cat doesn’t drink water from it.

The truth is that the cat will try to hunt down the fish and find the aquarium around the house. Hence, the possibility to hide your aquarium is not an option.

Here’s what you can do:

  • Place the aquarium as high as possible. Even though cats are jumpy, try choosing a location where there are no sofas or tables from where cats can get support.
  • Tightly lock the lid of the fish tank. This will prevent the cat’s access.
  • Limit the access ports to the aquarium
  • Place a towel or blanket on top of the aquarium to remove it from your cat’s visibility
  • Deter your cat through different activities and toys. Get your cat playful toys or bowls so that they enjoy drinking water from their own bowls instead of your fish tank.

In conclusion, remember that your cat should not drink aquarium water as it is highly toxic.

If your cat is not staying away from your aquarium, you can try the methods mentioned above.

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