Can Saltwater Fish Live In Freshwater?

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Written By Fun Fish Tanks

I Love my Fishes 

Are you wondering what would happen if you place your saltwater fish in a freshwater tank? As a beginner aquarium enthusiast, you’re curious to learn more about fishes. Ensuring that your pet fish gets a suitable environment is crucial for its wellbeing. If you’re introducing a new fish to your pet collection but don’t have a saltwater tank, you might want to know if you certainly need to arrange saltwater for it.

Generally, saltwater fish can’t live in freshwater. Euryhaline fishes are exceptions as they can withstand different salinities.

Typically, when you place a saltwater fish in freshwater, it will end up absorbing more water than it needs, leading to bloating and even death.

In other words, you can’t place your saltwater fish in a freshwater tank as that is fatal for it.

To understand why placing your saltwater fish in freshwater is so dangerous, you need to understand how a saltwater fish functions.

Why Can’t Saltwater Fish Survive In Freshwater?

Fishes osmoregulate according to the salinity tolerance of their body. The concentration of the salt solution in a saltwater fish body is too high for it to be placed in freshwater.

In such a situation, the fish will be unable to manage the amount of water it takes inside its body. This failure to osmoregulate will cause the fish to bloat and eventually explode.

Saltwater fishes in their natural habitat have a high amount of salt solution around them. Since saltwater is hypertonic in nature, fishes that live in it have to deal with water being sucked out of their body. To maintain the water content, these fish learn to drink more water.

A saltwater fish when placed in fresh water will continue to drink more water than it can tolerate. Moreover, instead of sucking water out, the hypotonic nature of freshwater will cause the saltwater fish to soak up water like a sponge. All these factors impede the saltwater fish’s ability to survive in freshwater.

Difference Between Saltwater And Freshwater Fish

A saltwater fish lives in saltwater which is hypertonic in nature. These fishes know that they need to drink a lot of water as the salty water around them sucks out water from their body. These fishes have a higher tolerance for salinity and can’t adjust to lower levels of salinity.

A freshwater fish lives in freshwater which is hypotonic in nature. These fishes know that water is continuously entering their body which makes it important for them to frequently urinate.

Balancing the level of water in their body is crucial to ensure that these fish doesn’t get saturated with water. Their low tolerance for salinity allows them to survive freshwater.

In other words, saltwater and freshwater fish have adapted themselves to survive in their respective environments.

Are There Any Fish That Can Live In Both Freshwater And Saltwater?

Euryhaline fishes have the ability to live in both freshwater and saltwater. There are two types of Euryhaline fishes: anadromous and catadromous.

An anadromous fish will travel up to a fresh water source like a river from the sea to spawn.

Examples of anadromous fish include salmonids, lampreys, striped bass, alewife, blueback herring and sturgeon.

A catadromous fish will travel down to a saltwater source like the sea from the river to spawn. Examples of catadromous fish include salmon, and eels.

How Long Can Saltwater Fish Live In Freshwater

If you decide to place your saltwater fish in freshwater, you can expect it to die anywhere between a few minutes to a few hours. It will slowly bloat towards death.

Fishes are very sensitive to the salinity of the water and can’t adapt to vastly varying ranges of salinity. Therefore, it is essential for the health of your pet fish to provide it with saltwater.

So Can Saltwater Fish Live In Freshwater?

The straightforward reality is that saltwater fish can’t withstand freshwater at all. If you want to kill your saltwater fish, all you have to do is place it in water with a low salinity level. The poor fish will soak up too much water, bloat, and die from exploding.


A saltwater fish can certainly not live in freshwater. When you place such a fish in freshwater, it fails to osmoregulate.

Being unable to manage the water content of the body causes it to soak an excessive amount of water. Eventually, a saltwater fish will die from bloating and exploding when placed in freshwater.

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