Why Is My Molly Hiding? (With 4 Easy Solutions)

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As a fish owner, I came to realize that molly fish are pretty hardy. They can easily survive in varying water conditions, including temperature and pH. However, more than once, I noticed that my molly fish keeps hiding behind plants and decorations. To determine whether my fish is dying, I began to research the topic pretty extensively. 

Molly fish typically hide when they share the same tank with aggressive tankmates, like bettas and barbs. However, that also happens when the water conditions are poor, including pH, ammonia, and toxins. Mollies also tend to hide in overcrowded tanks or when suffering from a bacterial infection.

As we move forward in this article, I will share a few useful techniques to treat a molly fish that is always hiding. That will allow you to prevent further deterioration, especially if your molly is suffering from an underlying disease.

Why Do Mollies Hide?

Is it normal for mollies to hide? Yes, it is. In the wild, mollies live in rivers, streams, and swamps with plenty of aquatic plants. They use the plants as shelter, and they have been known to hide under floating vegetation to escape predators’ attention.

To keep a molly fish happy, you must replicate its natural environment in the aquarium. That means adding items such as bushy plants, flowerpots, PVC piping, ornaments like sunken ships, driftwood, and rocks.[1]

Once you provide these items, don’t be so shocked once your molly starts using them to hide. Like most fish, hiding gives mollies peace of mind, and for the most part, it shouldn’t concern you. That being said, people buy fish because they want to admire the creatures as they explore their aquatic environment.

Mollies that spend most of their time hiding are no fun. More to the point, this behavior isn’t normal. Mollies should occasionally hide, not all the time. If your molly fish is always in hiding, things in the tank have gone wrong. Some common causes of hiding in mollies include:

1. New Environment

If your molly is new to the tank, the fact that it is hiding shouldn’t concern you. Some fish are quite confident when you first meet them in a store. But once you move them to your home tank, their behavior changes. 

They are intimidated and by the new environment, and this forces them into hiding.[2] Some fish are merely cautious. They are hesitant to trespass upon the territories of other fish. Again, this isn’t a problem. Hiding in new fish should only worry you if it persists.

2. Aggression

Mollies are peaceful fish that should be paired with equally peaceful fish. They are not compatible with species like bettas (too territorial) and barbs (too aggressive). They will nip at your molly’s fins, making life miserable and ultimately forcing it into hiding.

Where bullies are concerned, some fish will stop eating altogether. That is because they are too frightened to venture out of their hiding place during meal times because of the dominant fish’s presence.[3]

If one or more mollies rarely eat because they refuse to leave their hiding places, you can probably place the blame on an aggressive fish in the tank. Mollies that are being bullied tend to spend their time behind filters, plants, decorations, etc.

3. Schooling

Mollies are social fish that prefer to live in schools.[4] Because the males tend to harass their female counterparts, you have to keep your mollies in groups populated primarily by females. Schooling fish like mollies get lonely when they are forced to inhabit a tank alone. 

The isolation induces stress because the mollies do not feel safe. That prevents them from swimming confidently in the open. After a while, it becomes easier for the creatures to remain in hiding.

4. Water quality

Mollies are robust and adaptable fish that can live in various conditions, including freshwater, brackish, and saltwater. But there is a limit to what they can tolerate. Your job as an aquarist is to create the conditions they need to thrive. 

That means installing a decent filtration system that can generate a slow-moving current, keeping the temperature between 70 and 82 degrees F, the pH between 7.5 and 8.5, and the hardness between 10 and 25 dH.

Poor conditions in the tank will induce stress in your mollies. Stressed fish usually find relief by hiding. If the water conditions are responsible for your molly’s behavior, you will observe additional symptoms.

For instance, their breathing could become labored, a sign that ammonia levels have spiked. It could also signify oxygen deficiency or an unhealthy elevation in temperature.[5] You can conclude that the water conditions in your tank have deteriorated if multiple fish are hiding.

On the other hand, you cannot jump to this conclusion if only one molly is hiding. Inappropriate water conditions will affect all the inhabitants of your tank. To ensure that the water conditions are proper, you should perform measures once in a while (as I will explain later on).

Also Read: Stress In Molly Fish

5. Overcrowded Tank

A small tank with an abundance of fish is going to force your mollies into hiding. Overcrowding is terrible for all fish. It almost always induces stress. Larger and more potent fish react to overcrowding by becoming more aggressive. 

Some species will even kill their tankmates to secure the scarce resources in the tank. However, peaceful fish like mollies will respond by becoming timider and going into hiding to avoid the aggression manifested by their neighbors.

6. Disease

Some people think that fish like mollies go into hiding when they are about to die, but that isn’t entirely true. A sick molly will also go into hiding, especially if it is lethargic. It knows that it is weak and more vulnerable to attack from enemies, so it prefers to stay out of sight.

However, that isn’t always the case. Some sick mollies will hover in place or lie at the bottom. But it is also fairly common for them to go into hiding. Some of them might ultimately die while in hiding. That doesn’t mean that they went into hiding to die. It merely means that they died while hiding.

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

How to Keep Your Mollies From Hiding?

As was noted above, mollies that remain in hiding all the time are no fun. That is why you have to coerce them into the open by using methods such as the following:

1. Introduce New Fish Gradually

As mentioned earlier, some mollies will go into hiding either because they are new to a tank (or because you have introduced new fish to their tank). In such cases, you have to give them time to grow accustomed to their new environment. 

After a few days, they will grow comfortable enough to swim in the open. Do what you can to make the new tank inviting. That includes maintaining optimal water conditions and avoiding excessively bright lighting.

Another trick is to keep the new fish in the carrying bag inside the tank itself for a couple of hours. This way, it will be able to comprehend its environment without getting exposed to direct stress.

Keeping your fish this way will also solve the temperature differences issue. Often, the bag in which we’ve bought the fish is colder or warmer than the tank itself. By placing the bag within the tank, we get a gradual equilibrium.

2. Stick With Docile Tankmates

It would be best to pair your mollies with suitable tankmates like Guppies, Endlers, Platies, and Neon Tetras.[6] If your mollies are new to the tank, you can also limit older fish conflicts by rearranging the aquarium. 

That will disrupt pre-existing territories, allowing new mollies to secure a suitable home for themselves in the aquarium without clashing with older fish. If some of your molly’s tankmates are unreasonably violent, you can either remove them from the tank or insert a divider. 

Don’t isolate your molly only because it keeps clashing with its tankmates. That won’t serve any good in the long run. Also, mollies are exceptionally social. They need the company of other fish, and isolation will drive them deeper into hiding.

Also Read: 19 Great Neon Tetra Tank Mates

3. Ensure Proper Tank Conditions

If a molly is hiding because of the tank’s poor conditions, changing and improving those conditions will encourage it to come out into the open. That means keeping the temperature, pH, and hardness within the appropriate range.

Make sure that you clean all the driftwood thoroughly before you add it to the tank.[7] Otherwise, the tannins will soften the water (mollies like hard water). The tank should be at least 10 gallons in size to prevent overcrowding.

Also Read: Molly Fish Tank Size

You should also have one air stone for every ten gallons to prevent oxygen deficiencies; I personally got the Pawfly 1 Inch Air Stone (link to Amazon). It does a great job of oxygenating in my aquarium and is highly affordable. 

Keeping the lighting at medium brightness is also essential. Excessively harsh lighting will force the mollies into hiding. Also, don’t let the tank remain bare. Add a suitable number of plants and decorations. Make sure you avoid items with sharp edges that may cut your molly. 

Also, the current in your tank should be gentle. If it is more potent than your mollies prefer, you can weaken it by punching tiny holes through the output hose. If that doesn’t work, use a filter sponge to cover the filter’s nozzle. 

Don’t forget to test for toxins like nitrites, nitrates, and ammonia. For that, I highly recommend the API Aquarium Test Kit (link to Amazon). It contains several test bottles that will measure your pH, ammonia, nitrates, and nitrites within minutes. That is probably the most effective kit I’ve bought so far. 

If you detect toxins in the water, perform a water change. Mollies that are hiding because of poor conditions in the tank will emerge once the situation improves.

Also Read: Molly Fish Tank Setup

4. Disease Treatment

Observe your molly fish closely to determine whether or not it is sick or injured. If you notice worrisome signs such as loss of appetite, lethargy, and bruising, move the fish to a separate tank and initiate treatment. Once the fish is healthy, you can move it back to the main aquarium.

Be sure to quarantine new fish before you add them to your molly fish aquarium.[8] Otherwise, they might introduce diseases to the tank that will eventually afflict your mollies. As a rule of thumb, I suggest keeping new fish separated for three days.

However, if you suspect that it is already too late, I highly recommend checking the API MELAFIX (link to Amazon). Based on tea tree extractions, it is incredibly effective against bacterial infections and damaged fins.

It is worth noting that some mollies enjoy hiding. If your molly is happy and eats a healthy amount and hasn’t shown any signs of sickness and injury, you should probably leave it as it is. Don’t force it to come out in the open.

Either way, don’t take the hiding places away. A molly fish can survive in a tank with fewer plants and decorations and an abundance of open spaces. Yet, it won’t be happy and might struggle with anxiety and stress.

Also Read: 15 Molly Fish Diseases & Their Treatments

Do Mollies Hide When Giving Birth?

Mollies are live-bearers. While ordinary mollies are peaceful, pregnant mollies have aggressive tendencies.[9] They typically spend a lot of time near the heater. They also do a lot more hiding. In fact, in many cases, they only come out to eat.[10] 

Pregnant mollies usually spend more time hiding as they get closer to giving birth. As such, if you want to enhance your pregnant molly’s comfort, you must add a decent number of plants and decorations. That will allow the fish to feel secure.

Also Read: Why Is My Molly Fish Blowing Bubbles?


A molly fish that is hiding could be merely shy. Just like humans, fish also carry individual personalities. However, before concluding that, you should first eliminate potentially dangerous conditions. That includes bullying tank mates and diseases.

If your molly fish also appears sluggish and pale, you should probably take action. Start by isolating it in a separate tank. That will prevent potential diseases from spreading and relieve the stress coming from aggressive companions. 


  1. https://petcentral.chewy.com/aquarium-fish-hiding-places/
  2. https://www.thesprucepets.com/why-do-my-fish-hide-all-the-time-1380775
  3. https://kniselys.com/blog/58665/why-are-my-fish-hiding-now
  4. https://www.fishkeepingworld.com/molly-fish/
  5. https://aquariawise.com/why-your-aquarium-fish-is-hiding/
  6. https://www.aquariumnexus.com/best-molly-fish-tank-mates/
  7. https://www.vivofish.com/mollies/
  8. https://www.hartz.com/fish-behavior-basics/
  9. https://fluffyplanet.com/pregnant-molly-with-babies/
  10. https://aquariawise.com/how-long-molly-fish-pregnant-for/