Why Is My Molly Not Moving? (With 5 Quick Solutions)

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As a fish owner, I enjoy watching my fish swim. However, quite frequently, I notice things that get me worried. For example, a couple of times, I saw that my molly fish had stopped moving. As the years passed, I learned a few reasons for that issue and found ways to deal with it. Now, I am ready to share my experience.

Molly fish typically stop moving when exhausted and lack energy. That usually happens when the fish is sick or is exposed to the wrong water parameters, including elevated ammonia and nitrates. However, mollies will also stop moving when they are pregnant, constipated, asleep, or bullied.

As we move forward, I will teach you how to deal with mollies that stopped moving. I will also show you what signs are shown when the fish is about to die. If you notice those, that means you should act quickly to solve the issue.

Why Is My Molly Not Moving?

Mollies are active and social creatures. As such, if they are not moving, you should immediately investigate. Some potential causes of their listlessness include:

1. Your Molly is Pregnant

Is your molly fish female? If so, it may be pregnant. Mollies give birth to live babies, not eggs. You can tell that a molly fish is pregnant by looking for the gravid spot. The stomach will also expand, growing larger. If you look at the belly during the final stages of the pregnancy, you will see the eyes of the fry.[1]

The changes that a molly fish undergoes when it is pregnant are not limited to its physical appearance. The creatures will become more lethargic, eating slowly, swimming with less energy, and eventually avoiding other fish. In some cases, they stop moving. 

Some mollies will lie still at the bottom, while others will hover near an object such as a plant or decoration. You can blame this on fatigue and stress from the pregnancy. However, if you know that the fish is a male, there is another reason for the lack of movement.

Also Read: Pregnant Molly Fish 101

2. The Fish is Suffering from Oxygen Deficiencies

An oxygen deficiency can rob a molly fish of its energy. Oxygen deficiencies can occur as a result of too high or low temperatures. Water will release oxygen if it is too warm, although cold water is not necessarily better. It cannot absorb oxygen as effectively.

If the temperature isn’t to blame, you should look at the filter. Stagnant water cannot absorb oxygen at a sufficient rate to meet the needs of your tank’s inhabitants. Without an active filter to disturb the water, the mollies will become lethargic because they no longer have the energy to swim. In this case, they will either sit at the bottom or hover at the top, gasping for air.[2]

Also Read: Why Do Molly Fish Stay At The Bottom Of The Tank?

3. The Molly is Sick

If a fish as active as a molly is sitting or hovering in place, and you have determined that it isn’t pregnant, then it is most likely sick. Some diseases are worse than others. However, if left untreated, most of them can produce a listless, lethargic molly fish.

One example is ich. It causes white spots to appear on the fish’s body. Generally, that doesn’t sound so bad. However, the disease also robs the molly of its appetite, and a fish that doesn’t eat will eventually lose its strength.

Velvet is even more dangerous because it can cause lesions to appear on the molly’s skin.[3] Fin and tail rot are well known among aquarists, and so are the devastating consequences they can attract. 

Any disease that is allowed to progress will induce such distress in a molly fish that it will stop moving altogether. It would be best if you kept that in mind before dismissing your molly’s symptoms as mild.

Also Read: 15 Molly Fish Diseases & Their Treatments

4. Its the Fish’s Personality

How long has the fish been sitting or hovering in place? Does it look distressed? Is it eating on time? Does the molly fish spend most of its time in hiding? If you haven’t observed any concerning symptoms, you have to consider the possibility that your molly is just lazy.

Some fish stay still for long periods because they want to. If your molly fish always responds when you add food to the tank, it is probably healthy. You don’t necessarily have to take action if this lack of activity isn’t accompanied by additional clamped fins and gasping symptoms.

5. Your Molly has Aged

Molly fish are not immortal; they have an average lifespan of five years. As they age, they eat less and, as a consequence, lose weight. Some of them even become discolored, and their eyes begin to bulge. On occasion, aged mollies may float on their side. 

However, some fish do not physically manifest their old age. Instead, they will drop dead very suddenly, without warning. But in many cases, they start by slowing down, becoming listless and lethargic.[4] You should bear this scenario in mind if you own your molly for quite some time.

6. Inappropriate Water Conditions

Are the conditions in your molly fish tank appropriate? It would help if you asked yourself that because molly fish are sensitive to extreme temperatures, not to mention the wrong pH and hardness. They may respond to the poor conditions in their tank by swimming erratically or becoming violent. 

But eventually, their strength will abandon them, and they will become inactive. That is common in tanks that are overstocked, too small, and poorly maintained. If your aquarium water is so dirty that it is cloudy, your molly’s lethargy shouldn’t surprise you.

7. Swim Bladder Disease

Fish use the swim bladder to control their buoyancy in the water. When an injury or disease compromises the swim bladder, the fish’s ability to swim will suffer. Swim bladder disease causes some fish to sink to the bottom. Others will swim in irregular angles. But in some cases, the ailment makes swimming such a struggle that the exhaustion causes the fish to become inactive.  

8. Constipation and Overfeeding

Does the fish look bloated? If so, you most likely overfed him, and he needs a moment to digest the food. Sometimes, overfeeding causes constipation, which can also hinder a molly fish, causing it to sink to the bottom. 

Constipation is a common cause of swim bladder disease. As mentioned earlier, swim bladder disease can lead to exhaustion, ultimately forcing your molly to hover in place. The fish will also appear lethargic and sluggish.

Also Read: Molly Fish Constipation

9. Stressful Environment

Stress is terrible for mollies. It is often associated with hiding and loss of appetite in fish. But it can also cause listlessness in your mollies, especially if it persists to the point of compromising the fish’s immune system and leaving it vulnerable to infections.

If your tank features some aggressive tankmates, like Angelfish and Oscars, likely, your molly is not moving because of them. The fish may choose to hover in place, in a relatively safe place. This way, it won’t have to face its bullies.

Also Read: Stress In Molly Fish

10. The Molly is Sleeping

If you did not know, fish sleep. However, they don’t have eyelids, so they can’t close their eyes.[5] Fish can sleep at any time of the day or night. That being said, they prefer to sleep at night when the lights are off.

Even though their eyes remain open, sleeping fish will become inactive. Some stop moving altogether. Others will remain in motion, but their movements will become slow and sluggish. You can tell that the fish is sleeping by irritation. Knock on the tank’s glass and see whether the fish wakes up.

How to Deal with Mollies that Stopped Moving?

If your molly isn’t moving, you have to consider the possibility that it may be dead. Observe it closely. If the gills are moving, then it is still alive, in which case you still have the option of treating it using the following:

1. Check the Water Parameters

I highly recommend ensuring that the parameters in the tank are ideal for molly fish. That includes the temperature (72-78 degrees F), pH (6.7-8.5), and hardness (between 20 and 30KH).[6] Also, make sure that heaters and filters are still working.

You cannot depend on water changes alone to keep the tank clean, and neither can you rely on the ambient temperature to maintain the tank’s conditions. It is also vital to check the water for toxins, including ammonia, nitrates, and nitrites.

On that matter, if you don’t already own it, I highly recommend getting the API Aquarium Test Kit (link to Amazon). That useful bundle will measure your pH, nitrates, nitrites, and ammonia within five minutes and signal if something had gone wrong. I’ve been using this one for years with great success.

As was mentioned above, the ideal temperature for mollies is between 72 and 78 degrees F. However, the temperature should also remain stable throughout the day. Drastic fluctuation will stress your mollies and the rest of the fish. 

For a stable temperature, I highly recommend checking the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon). After trying multiple heaters, I can say that the Cobalt Aquatics is the only one you can trust to keep the water stable.

Also Read: Molly Fish Temperature

2. Replace the Tank’s Water

A water change is an answer to many of the problems that manifest in an aquarium. A water change will eliminate pollutants and remove toxic elements like ammonia. If the fish is already listless, you should perform small water changes over the next several days.

It would be best to avoid significant water changes because they will induce even more stress. Once the fish recovers, you should schedule regular water changes to prevent the water’s quality from deteriorating. 

3. Oxygenate Your Aquarium

You can overcome oxygen deficiencies by agitating the water. A decent filter can do this, but you should also add a few air stones. They will ensure that all the corners of the aquarium receive oxygen. I personally use the hygger Aquarium Air Stone Kit (link to Amazon).

Maintaining the appropriate temperature is just as important. That is why it is better to keep the aquarium away from windows. Direct sunlight can cause the temperature to spike. The same is true for excessively bright lighting.

Also Read: Do Molly Fish Need A Bubbler?

4. Eliminate Stressing Factors

Some aquarists tackle stress by giving their fish a salt bath, which can have a calming effect on fish. However, with mollies, it is often enough to eliminate the sources of stress. That includes toxins, cramped conditions, and bullies. 

It would help if you also gave them places to hide. You can quickly achieve that by adding a few plants and decorations. These will allow your molly to stay out of sight in case the tank features aggressive tankmates.

5. Dealing with Swim Bladder Disease

People typically treat this ailment by forcing the molly fish to fast for a few days (three or four). That is an effective response to fish that are constipated. Once this period elapses, you should give the fish peas that have been cooked and peeled. They will eliminate the blockage in the fish’s digestive system.[7]

If the fish is sick, your response will depend on the illness in question. Though, in many cases, you are encouraged to quarantine the fish while you attempt to diagnose its symptoms. Then, make sure to consult an aquatic veterinarian.

Also Read: Molly Fish Swim Bladder Disease

How to Tell if Your Molly is Dying?

You can tell that your molly fish is dying when it develops typical symptoms, such as rapid gill movement, lethargy, and weight loss. Also, dying mollies may develop lesions throughout their body. Dealing with it involves quarantining the fish while adjusting the water parameters.

Some aquarists are a little too quick to dismiss the signs of illness in their fish. They do not realize that some diseases are more than capable of killing their fish. The following signs and symptoms always concern aquarists:[8]

  • Sores – The presence of sores, swellings, and lesions on a fish’s body is troubling because they mean that the fish is losing a fight with a bacterial infection, the kind that can affect the other fish in the tank. The same can be said for bumpy growths.
  • Gill Movement – If your mollies’ gills are racing, it means that the fish is struggling to breathe. Because mollies must breathe to survive, labored breathing is a sign that they need immediate help.
  • Weight Loss – Weight loss is another sign of imminent danger. It shows that the fish isn’t eating quite as much as it should. Weight loss can also point to a parasite, not to mention ailments like stress. Either way, if the fish keeps shrinking, it will die.
  • Lethargy – An inactive fish is either mentally traumatized or too physically exhausted to move. Lethargy usually goes hand in hand with weight loss. Lethargic fish eventually lose their appetite, which can only make them weaker in the long run.
  • Color Loss – You can use a fish’s color to track its health. A fish’s colors will fade even as its health fails. In other words, the paler the fish, the more profound its condition.

Also Read: Why Is My Molly Shaking?


Mollies stop moving for several reasons. If that happened in your tank, start by checking the fish more closely. Look at its belly and try to determine whether it is pregnant or constipated. You should also check the water parameters, including pH, temperature, ammonia, and nitrates.

If you rule out all the possibilities, it could be that the fish stopped moving because of its personality. Some fish are less active than others, including fish within the same species. If the fish looks healthy and the water conditions are okay, you may leave the fish as it is.


  1. https://www.cuteness.com/article/tell-molly-fish-pregnant
  2. https://www.hartz.com/fish-behavior-basics/
  3. https://www.aquariumnexus.com/molly-fish-diseases-parasites-remedies/
  4. https://aquariumsphere.com/what-are-signs-of-old-age-in-aquarium-fish/
  5. https://wonderopolis.org/wonder/do-fish-sleep-with-their-eyes-open
  6. https://www.fishkeepingworld.com/molly-fish/
  7. https://pethelpful.com/fish-aquariums/STOP-Your-Pet-Fish-May-Not-Be-Dead
  8. https://www.petsmart.com/learning-center/fish-care/is-my-fish-sick/A0029.html