Converting Freshwater Mollies to Saltwater {Full Guide}

Have you seen saltwater mollies before? Have you ever thought of converting your freshwater mollies to saltwater mollies?

Can you convert freshwater mollies to saltwater? Mollies, especially the black-colored mollies can be converted to saltwater through the process of acclimatisation.

Converting Freshwater Mollies to Saltwater

Is It Possible Acclimating Mollies to Saltwater?

Yes, it is possible to acclimatize Mollies to saltwater. Mollies are good at adjusting to extreme and sudden changes. Hence, they can adapt to saltwater.

There are two mollies said to have high adaptability to saltwater, the Sailfin and the Giant Sailfin mollies.

Some people acclimatize freshwater mollies by dropping them directly into the saltwater and allowing it to adjust to the water over time.

Others use airlines to suck out and replace the water slowly.

How Do I Change my Freshwater Tank to Saltwater?

You can change your freshwater tank to saltwater using an airline to suck out and replace the water.

  1. First, insert one end of the airline in the water surface and hold it in place to not fall out.
  2. After inserting the airline into the water’s surface, set a drip rate by tying a knot to a part of the airline. The tighter the knot, the slower the drop rate of the airline.
  3. Once you are done tying the knot, suck gradually on the other end of the pipe to get the water moving.
  4. Make sure to remove the pipe from your mouth the moment the water starts moving to avoid the water getting into your mouth.
  5. As you remove the other end of the airline from your mouth, channel it to a bucket so that the water will pour into the bucket as it comes out gradually.
  6. Once the water is done draining from the tank— it can take up to an hour— gradually replace the water with your already prepared saltwater that matches the water temperature in the bucket to average height.
  7. After replacing the water, put off the lights in the tank, and avoid feeding the mollies for the meantime so that they can settle down in the saltwater.

Post Checks

Observe the fish and ensure they are in good condition. Look out for signs like heavy breathing and distress in the mollies.

If any of them suffer from those symptoms, separate them into a mini tank. If you notice any occurrence of death, remove the dead fishes as quickly as possible to avoid contaminating the water and making it unsafe for others.

It is important to note that the ability of your mollies to transition successfully into saltwater mollies depends on their species.

Hence, it is best to go for the recommended species; there is, however, no harm in trying other species.

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What Salinity Can Mollies Live?

Mollies can live in salinity as high as 1.025. however, it depends on the species of mollies you are breeding. Black sailfin mollies are said to be the ones with high tolerance— they can adapt to sudden changes in salinity.

When mollies transition successfully to saltwater, at first, they are reserved, not being active like their usual self, but after some time, mostly an hour, they resume their normal activities.

How Long Can Mollies Live in Saltwater?

Generally, mollies do not live too long; they are widely known to live for five years. However, their lifespan depends on the nature and condition of the tank.

For a mollie to survive in a saltwater tank, it means that the fish has adjusted to the state of the tank, and it can live for 3-5 years.

If you are thinking about converting freshwater mollies to saltwater mollies, you should only be bothered about having successful transitions.

Once the change is successful, your mollies have adjusted to the water type and will normally thrive if the tank’s condition is favorable to them.

Are Saltwater Tanks Hard to Maintain?

No, saltwater tanks are pretty easy to maintain. All you need to do is maintain a balance in the temperature and salinity of the tank.

Are Saltwater Tanks Hard to Maintain

To maintain saltwater tanks, change your water regularly, maintain biological filtration, scrub algae regularly, check the quality and temperature of the water daily, and carry out every other maintenance activity necessary for a tank.

If you are thinking of changing to a saltwater tank, go for it. There is no special treatment or stress attached to having a saltwater tank.

You only need to maintain the chemical balance, biological filtration, and temperature of the tank for the fishes and other vertebrates to successfully thrive.

Should You add Coral or Fish First?

For a practical answer, add the one that is less sensitive before adding the others. Mollies, especially the Black mollies, have a high ability to adapt to changes compared to corals.

It makes them the best choice to add first. Suppose we are to consider cost, taking mollies, for instance.

They do not cost much, which makes the impact of losing them to death less impactful to your pockets when compared to corals. Adding fish first is a safer way to play with your money.


Converting freshwater mollies to saltwater can be pretty straightforward. However, there is no guarantee for how many mollies will survive; it is like a trial experiment.

Dropping the freshwater fish directly into the saltwater has shown not to have much success compared to the fish’s acclimatization.

You need to patiently and gradually acclimatize the fishes for up to an hour so that they can gradually adjust to the change in salinity.

When acclimatizing the fish, be very observant, taking note of the changes in the mollies. If you notice any sick or dead mollies, remove them immediately to avoid contaminating the other fishes.



Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.