Do Fish Drink Water? If yes, How? – Do Fish Ever Get Thirsty?


We all know that fish live underwater but do they drink it?

Such a simple question!

Or is it?

I am sure, like me, most of you haven’t really even thought about this.

I was oblivious to the whole fish drinking water thing until my four-year-old nephew asked me if fish needed water as we all do?

So me being me, couldn’t rest until I figured this dilemma out.

So, Do Fish Drink Water?

The short answer is yes, they do. But it depends on the kind of fish you are talking about. Freshwater fish do not technically drink water, as it could lead to their blood getting too diluted. Saltwater fish, on the other hand, do drink a lot of water to keep themselves hydrated.

Let’s dig in…

How do fish drink water?


Do Fish Get Thirsty?

Now whenever we talk about drinking water, the term thirst comes to mind.

We humans, do not drink until we feel thirsty.

Feeling thirsty is just a way our body uses to signal to us that it needs water to function.


This gets a little complicated when it comes to fish.

Fish live in water all year round, how could a creature that is always surrounded by water ever get thirsty?

Would you get hungry, if you lived a house full of pizza?


This is not as simple as it seems.

Freshwater and saltwater fish both have different anatomies and hence different behaviors when it comes to drinking water.

Fish do not really need to feel thirsty to drink.

It’s merely a reflex that occurs without actually requiring a conscious decision on their part.

So fish probably never feel thirsty like we humans do.

Why Fish Can Drink Salt Water And We Can’t?

Drinking Mechanism of Freshwater Fish

Freshwater fish actually have high levels of salt in their blood as compared to the water that they are surrounded by.


There is a risk of their blood getting diluted if they drink water.

This is precisely why freshwater fish do not drink water.

Instead, they make use of osmosis.

Freshwater fish absorb water through their gills as well as their skin.

They also urinate a much more dilute liquid to get rid of any excess water.

Drinking Mechanism of Saltwater Fish

The blood of saltwater fish is much more dilutes when it comes to salt, as compared to the water that surrounds them.

The poor creatures are always at risk of dehydration.

This is why:

Saltwater fish need to drink water actively.

They have astonishing gills that help them drink the salt water, process it and then eliminate all the excess salt via excretion.

Fish Who Live in Both Environments

Though there aren’t very many, there are some fish who migrate between saltwater and freshwater, like salmon.

Do they drink the water?

How do they survive in two such different environments?

Born in freshwater, the young salmon undergoes three major changes before leaving its freshwater nursery for its saltwater home.

It begins by drinking lots of water.

Their kidneys decrease their output, secondly.

Most importantly, mechanisms in the gills begin operating reverse, ridding the fish of salt instead of taking it in.

When the adult salmon returns, it will spend a few days in a neutral environment called the intertidal zone (a marine environment in the foreshore and seabed area that is exposed to air at low tide and submerged at high tide) while the changes it made in infancy reverse themselves so the fish can live in freshwater again.

So yes, the fish who live in both environments do drink water.

Do Other Water-Dwelling Creatures Drink Water?

We know that fish are not the only water-dwelling creatures in existence.

What about their marine neighbors?

Do whales, dolphins, and even turtles drink water?

We know that they, like all creatures, need water to remain hydrated.

What may not be as clear is whether or not these animals drink the water they live in.

Do Whales Drink Water?

Whales are classified as marine mammals.

They need to stay hydrated by drinking water from their surroundings or getting it from their meals.

Whales have rather huge kidneys which allow them to excrete any excess salt, without losing a lot of water.

And another thing:

Whales do not sweat, and they do not lose any water when they breathe.

We humans, lose a lot of water when we breathe.

The air above the ocean is full of water, and so whales do not lose much water this way.

Do Dolphins Drink Water?

Dolphins, just like whales are also characterized as marine mammals.

One theory is that dolphins consume water from their food.

Squids, other fish and octopus all already contain lots of water.

When the dolphins devour these aquatic animals, they extract the water from their bodies which is much better than directly drinking saltwater.

Another theory is that when dolphins devour their prey, they also take in the surrounding water.


Dolphins have a highly advanced filtration system.

This fantastic mechanism allows them to easily extract additional salt from their urine which helps them to separate the salt from the saltwater that they drink.

Do turtles drink water?

Turtles are reptilian creatures who can survive on land and in water.

Because they do spend a good deal of their time on land, turtles do need to stay hydrated.

This means that yes, turtles do drink water.

Turtles most often drink the water they swim or wade in, although turtles who reside mainly in the salty ocean have to filter out the salt in their water.

For this purpose, these turtles have a special gland in their eyes called salt glands.

When they drink the salt water, the salt enters their blood and is carried through their bloodstream to the salt glands.

The salt glands then produce a solution that is twice as salty as the water the turtle consumed, which then exits the turtle’s body through the corner of their eye and is washed away.

Because turtles do drink the water they swim in, a turtle who is kept as a pet will need to have their water dish cleaned and replaced regularly.

While water in nature filters out the animal waste deposited by the creatures who live in it, stagnant water like those found in pet bowls does not.

For this reason, it must be replaced regularly or risk damage and illness to the turtle.

What Happens When Marine Mammals Consume Too Much Saltwater?

This situation is very complicated.

If marine mammals consume too much salt, they begin to suffer from fatal health conditions such as kidney problems, liver damage as well as physiological issues.

This is why:

It is essential for marine mammals to filter and excrete the additional salt that they consume when they take in saltwater.

It helps them avoid various organ issues.

Do Fish Pee?

We all know that fish poop.

I mean, the poor state of your fish tank just after a week of neglect literally proves this.

But the question is, do they urinate?

If you stop cleaning your tank, and it begins to smell like ammonia.

Well, there is your answer.


Fish do pee, but different kinds of fish urinate in different ways.

Fish, basically urinate constantly.

How Do Fish Urinate?

Most fish urinate either via their urine pores or their gills.

The fish that urinate via their gills eliminate urine that has been filtered by their kidneys.

On the other hand:

Saltwater fish urinate using their gills while the freshwater fish urinate using their urinary pore.

As discussed before, saltwater fish live in an environment where the salt concentration in their surroundings is much higher than in their blood.

This is why saltwater fish take in a considerable amount of salt, and they need to eliminate it.

Freshwater fish, on the other hand, need to eliminate the excess water that they devour.

Fish Kidneys

All fish possess two kidneys.

The posterior kidney filters the waste that goes out to the urinary pore while the head kidney eliminates waste via the gills.

In saltwater fish, the kidneys excrete ions and conserve water and eliminate most of the waste through the gills.

In freshwater fish, the kidneys to the exact opposite.

They eliminate water and save ions.

Fish Urine

The major component of fish urine is ammonia.

The ammonia leaves the body of the fish via the gills, and this again depends on the kind of fish in question.

And another thing:

Fish urine also consists of organic acids creatine and creatinine, amino acids and minute amounts of urea.

Freshwater fish urine contains tons of water while the urine of the saltwater fish contains great amounts of salt.

Saltwater fish do not produce a large amount of urine but what they do excrete is highly concentrated.

Freshwater fish, on the other hand, produce lots of urine.

What Color is Fish Urine?

The urine of fish is very different from humans.

Fish urine is usually black or very light black.

Kidney Disease and Urinary Tract Disease among Fish

Just like us, fish can also suffer from urinary tract as well as kidney diseases.

These diseases develop in the body of the fish due to a parasite known as Renal Dropsy.

Renal Dropsy, is very common among carp species and goldfish.

Fish that are affected by such diseases showcase swelling in their abdomen from accumulated fluids as their kidneys fail.

Another parasite is known as Sphaerospora angulate also causes kidney disease among carp species.

The abdomen of the fish swells, as well as their eyes.

The fish that showcase these symptoms do not live for more than six months.

Proliferative kidney disease affects young, commercially-grown trout and salmon.

In addition to this:

Fish also become ridiculously lethargic and sluggish.

Fish Pee to Exert Dominance

According to several studies, fish pee on other fish when they want to let the other fish know who is in charge.

We have learned:

We all know that fish live in water.

Some live in fresh water, some live in salt water – but they all live in water.

We also know that life cannot exist without water, and we need to drink water to stay properly hydrated.

But since the fish live in water, do they drink it?

What about other animals that live in the water – do they drink it? If they do, how? And if they don’t, how do they survive?

While some fish can survive outside of the water for up to several days, they will eventually die.

This is because their lungs are not set up as mammalian lungs are.

When a mammal takes a breath, our lungs fill with air and specialized cells filter out the oxygen that we need.

Our lungs need to stay dry and fluid-free for this process.

Fish, on the other hand, take water in through their mouths and use their gills to filter the water out while retaining the oxygen that they need to breathe and oxygenate their cells.

The oxygen then spreads to the fish’s blood and travels onto the fish’s cells.

All creatures need water to survive, even if they live in water.

How they get this water depends on which type of watery environment they live in and their biology.

Saltwater creatures need to maintain a balance of salt in their bodies which is made more difficult by their salty environment, and so have adapted their bodies to filter out dangerous levels of salt.

Freshwater creatures don’t have this difficulty but do have to be sure to maintain a safe level of salt in their own bodies.

Mammals who live in the water have the added need to maintain dry lungs while also remaining hydrated and keeping their salt levels in their bodies at a safe level.

All of them, however, still need water to survive, whether they drink it or absorb it.

Related Questions

Can you use regular tap water for Betta Fish? Yes, you can. Never use distilled water as it does not contain enough dissolved oxygen or minerals to keep your Betta Fish healthy. Tap water is actually your best bet. Allow the tap water to breathe out the chlorine for about a day and then warm it to room temperature. Using a water treatment product also helps.

Do Fish Cry? Fish do not cry as humans do. They lack the cerebral cortex and limbic system that generates emotional responses in humans. But scientists have discovered that fish do cry, only vocally.

Do Fish Get Bored? Fish do get bored, especially goldfish. Their behavior may be mistaken as a lack of oxygen or that they are begging for food. Goldfish seldom beg for food and if they do not have the right amount of oxygen they will just remain at the surface of the fish tank. You can get companions or plants for your fish to keep them entertained.


Other Sources:

  • How to care for pet fish?
  • Best fish species for beginners
  • Large Aquarium Hacks

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