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Can Guppies Live in Saltwater? (6 Steps Acclimatization Guide)

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As a fish owner, I have both fresh and saltwater tanks. Quite frequently, I wondered whether I could make some exciting mixes. For example, I wanted to know whether my freshwater guppies could live in the saltwater tank. To answer that, I started researching the topic pretty extensively.

Guppies can live in saltwater tanks with salinities ranging from 39.0% to 58.5%. However, introducing them to saltwater too abruptly can cause dehydration and possibly death. Instead, they should pass an acclimatization process, in which the guppies are gradually exposed to salt in a dedicated tank.

As we move forward, I will teach you what to do so that your guppy can get used to saltwater without suffering. That includes a step-by-step, short guide that requires an acclimatization tank, a tube, and a check valve.

Also Read: 21 Facts About Guppies

Can Guppies Survive in Saltwater?

Yes, guppies can live in saltwater and tolerate salinities up to 58.5%.[1] They are categorized as freshwater fish in some circles, but they are more than capable of surviving and thriving in salt water.

That is what you should know:

1. Saltwater vs. Freshwater Fish

Saltwater fish can survive in water bodies with high concentrations of salt because they have internal mechanisms that enable their kidneys to force excess salt out of their bodies.[2] Because salt attracts water, the high salt content in a tank causes water to flow out of the fish. 

On the other hand, low salt content causes water to flow into the fish. In a freshwater tank, there is more salt in the fish than there is in the water. If you place that same fish in a marine tank, you will create a situation in which the water has more salt than in the fish’s cells. 

Consequently, water will rush out of the fish’s body, dehydrating it, and possibly killing it. That is the primary reason why freshwater fish can’t live in saltwater. However, things aren’t black and white. In some cases, freshwater fish can live in saltwater, although the tank shouldn’t be too salty.

2. Guppies’ Ability to Adapt

Guppies have a reputation for being hardy fish that can survive in a variety of water conditions. They can tolerate dramatic shifts in salinity, pH, and temperature. They can even survive in environments that are up to 150 percent of average seawater salinity.[3]

Even though many aquarists keep them in freshwater tanks, they are just as comfortable in brackish water, which combines both freshwater and saltwater. Can guppies live in full saltwater? Yes, they can. But you can’t just throw them in a saltwater tank. 

Instead, they should be exposed to a process that will acclimate them to their new marine conditions. Otherwise, they will die just like any other freshwater fish in saltwater. A guppy that has acclimated to seawater will develop the osmoregulatory functions required to process the high salt content.[4]

3. Salt as a Remedy for Sick Guppies

Many aquarists add salt to freshwater guppy tanks. Some do this because they want to use the salt as a buffer to maintain a constant pH. Other aquarists use salt to enhance the guppy’s ability to combat parasitic and bacterial infections. 

That typically includes low concentrations of salt, about one teaspoon for each gallon of water. The salt typically kills the bacteria or fungi in the same way it may kill fish. But the concentrations needed to kill infections are much lower than those needed to harm fish.

However, that isn’t always necessary. If you are contemplating the notion of adding salt to your guppy tank, you should only do so if the water is soft and doesn’t feature enough minerals. On the other hand, if the water is hard (it has many minerals), salt isn’t necessary.

4. Caution

The average guppy can tolerate one tablespoon of salt for every ten gallons of water. While guppies are adaptable, salt in excess quantities will harm their kidneys, killing them in the long run. As such, you have to pay close attention to the amount of salt you add to your tank.

You also require consistency. Once you have decided to add salt to your guppy tank, you must maintain that same concentration even when you perform a water change. If you can’t maintain that consistency, you shouldn’t add salt to the tank in the first place.

How to Acclimate Guppies to Saltwater?

Acclimating guppies to saltwater involves these steps:

  1. Get a tank that features at least two gallons for each guppy.
  2. Fill the tank with fresh water, one gallon per guppy.
  3. Connect the container to the saltwater tank using a tube and a check valve.
  4. Flow saltwater to the acclimatization tank using the tube, one drop per second.
  5. Once filled, empty the tank and repeat the process once more.
  6. Move your acclimatized guppies to the saltwater tank.

As was noted above, guppies can only live in saltwater once you acclimate them. You may introduce guppies to a tank that features one tablespoon for each gallon of water without acclimatization. As was mentioned, that is a treatable dose for diseases and infections.

However, if you have a saltwater tank with fish like clownfish or seahorses, you need to follow a specific process. If you introduce your guppies as they are to the saltwater tank, they will probably die in an hour. 

To avoid that, follow the process of acclimatization below:

Step 1: Choose the Right Tank 

Your first step would be getting a clean container that is large enough to accommodate your fish. Where one guppy is concerned, two gallons should do. However, more guppies will need more space. Stick to two gallons of water for each guppy you acclimatize. 

Add one gallon of fresh water to the tank for each guppy. I recommend using the water your guppies already have. That will prevent stress related to abrupt water changes, which could kill your guppies on its own. Then, place the fish in the container.

Step 2: Get a Tube and a Check Valve

Get an air pump tube and attach an air control valve to one end. The valve allows you to regulate the volume of water moving through the tube. If you already have an air pump, you could merely get the Pawfly Aquarium Air Pump Accessories (link to Amazon).

That kit also includes two airstones that can contribute to oxygenation in the saltwater tank (not the one we are talking about in this section). Aerating the saltwater tank will give your guppies better conditions and ease their acclimatization process.

Step 3: Flow Saltwater to the Acclimatization Tank 

Place the other end of the tube in a saltwater tank. The goal is to siphon water from the saltwater tank to the container. However, that can only work if the container is positioned lower than the saltwater tank. Try to position it six inches lower.

Place your mouth on the end of the tube leading into the adapting container and start sucking. Do so until the saltwater travels out of the tank and rushes down to your mouth. It doesn’t have to reach your mouth. Halfway, water should flow on its own.

Once the water begins to flow, it will continue to do so without any assistance from you, mainly if your entire setup is correct. Put the lower end of the tube into the adapting tank. It would be best if you keep it above the water level so oxygen will dissolve more naturally.

Step 4: Control the Flow Rate

That is where your valve enters the picture. Use it to adjust the rate at which the saltwater enters the container. Limit the flow rate to 1 drop of saltwater per second. That sounds slow, but it is necessary to protect the fish from unnecessary harm.

The beauty here is that your guppies will never experience salt concentrations that are higher than required. Gradually, the water will get closer and closer to the saltwater aquarium conditions. That is our primary goal.

Step 5: Let the Tank Fill

At this point, it would be best if you waited until the container had filled. However, once this happens, you shouldn’t be quick to celebrate. You haven’t done yet since your fish haven’t been fully acclimated. All you have at that moment is brackish water. 

Now, empty the container until it has just an inch of water left. After this, you can start the process all over again. You may increase the rate to 3 or 4 drops a second. By doing so, you will get your acclimatization tank even saltier.

Step 6: Move Your Guppies to the Saltwater Tank

Once the container fills a second time, you can successfully conclude that the guppy has been acclimated. The container has full saltwater at this point, and your guppies have adjusted to the conditions in the saltwater tank.

Now, you may move the fish to the saltwater tank. However, because of size differences, the two tanks might not be at the same temperature. Therefore, it would be best to place your guppies in a plastic bag containing the water from the acclimatization tank.

Then, put the bag in the saltwater tank without opening it. That process mimics the one of buying new fish for your aquarium. That allows the temperature to reach a necessary equilibrium. Don’t let this small detail ruin your entire hard work.

How Long Can Guppies Live in Saltwater?

Guppies have a lifespan of roughly two years in freshwater, and that shouldn’t change in saltwater. If they have been acclimated appropriately, they will live normally. However, if moved to a saltwater tank without acclimatization, they won’t survive more than a few hours.

That is what you should know:

1. Adaptations and Complications

It takes 12-24 hours for guppies to acclimate to a new saltwater tank. However, there is no guarantee that they will survive in saltwater without complications. That is why you are encouraged to observe them closely after moving them to a saltwater tank.

Bear in mind that a guppy can still grow sick and dehydrated in a saltwater tank even after being acclimated. Once you observe signs of distress that might suggest dehydration, move the fish back to a freshwater tank. Do this immediately. Don’t bother with acclimation.

Typically, a dehydrated guppy will appear lethargic and sluggish. It is also likely that it will frequent the lower sections of the tank and hide behind plants and decorations. That is because the fish feels stressed and seeks shelter from its tankmates.

2. Possible Death

Death by dehydration is unpleasant. Most freshwater fish will perish in a saltwater tank in less than an hour. It is a torturous and traumatic experience. If your guppies have failed to acclimate to their new saltwater environment, it might take hours for the signs to manifest, 27 hours in some cases.

That is why you can’t blame some aquarists for missing the signs, including wobbling and swimming at the surface. It never occurs to them to keep a close eye on their guppies after the first few hours following their introduction to a saltwater tank.

Also Read: How Many Guppies In A Fish Tank?


Guppies have the potential to survive in saltwater tanks, although they shouldn’t be introduced all at once. Moving a freshwater guppy to a salty tank as it is will end up with a dead guppy within a few hours.

Instead, one has to conduct in which the guppy gets accustomed to saltwater gradually. Using a tube with a check valve can get this done. That involves connecting the saltwater tank to the acclimatization tank while letting the water flow relatively slowly.

Bear in mind that the longer the guppy gets accustomed to salted water, the more it is likely to survive along with saltwater fish. It would help if you weren’t quick on that. Let the guppy’s body reach the right osmoregulation point it requires.