Why Do Molly Fish Stay At The Top Of The Tank? 

Has it been tough for your fish to stay on the ground? Are they unable to swim effectively? Have your molly’s appearances changed recently, if so? And does your molly have any trouble swimming?

Due to the poor water quality and lack of oxygen, molly fish like to stay near the top of the tank. In the worst situations, it floats to the surface when it is affected by constipation or swim bladder disease.

Therefore, if you want to find out more about the causes of your molly’s behavior, stay reading since everything is detailed in depth below.

Why Do Mollies Remain at the Tank’s Top?

Despite being little fish, mollies are quite active. They require as much room to explore as you can provide. They shouldn’t spend all of their time up top, and if they are, one or more of the following factors are to blame:

Why Do Mollies Remain at the Tank's Top

1. Swim Bladder Disease is What Your Molly Has

The molly fish uses its swim bladder to maintain its optimum depth in the water while swimming upright. Every time the swim bladder quits functioning, the molly fish exhibits irregular swimming behavior.

It could periodically fall to the aquarium’s bottom, where it will remain because its swimming ability has been compromised. Occasionally, it will float to the top, where it will remain since, as was already mentioned, its ability to swim has been impaired.

Swim Bladder Disease

Swim bladder disease may develop when the swim bladder is squeezed by other organs. It can also be brought on by infections, overeating, and constipation. If your molly suddenly changed how it swam, you should presume that her swim bladder is to blame.

2. Not Enough Oxygen Is Being Given to the Fish

The oxygen content of the water should be your top priority if a fish begins to congregate near the surface. Fish utilize their gills to get oxygen out of the water, which explains why. Naturally, the tank’s surface is how oxygen is introduced.

In the case of a sudden decline in oxygen levels, the molly’s only sane plan of action is to swim to the surface, where oxygen levels are still sufficient.

Lack of Oxygen

Similar to how humans gasp for breath, molly fish that are hanging out at the top due to a lack of oxygen will also gasp for air, opening and closing their mouths rapidly. If the oxygen levels in the tank do not increase, the molly will eventually become drowsy since it will not have the stamina to swim as aggressively.

The following are some common causes of an oxygen deficit:

  • Temperatures: At high temperatures, water cannot contain as much oxygen as it does at low temperatures. If your tank overheats, reducing the oxygen concentration of the water, your fish may seek oxygen near the surface. This is typically caused by the summer heat, a faulty heater, or extremely bright lights.
  • Stagnation: Even when enough oxygen dissolves into the tank, the water needs to be stirred up to make sure that it is distributed equally throughout the aquarium. Some areas of the water will become oxygen-deficient if the water is allowed to stagnate. Tanks without filters or pumps are susceptible to stagnation.
  • Overstock: You can’t afford to overstock your tank with mollies. They will exhaust all the oxygen, resulting in a shortage that will make some of them frequently visit the tank’s top. That also occurs in tanks that have too much vegetation in them.
  • Live plants have the capacity to create oxygen. To increase the amount of oxygen in aquariums, people add them. Live plants, however, can only produce oxygen when they are exposed to light. They literally use up oxygen at night. There won’t be enough oxygen in the aquarium if there are too many plants and not enough light.
  • Waste: The amount of oxygen that is available in the aquarium could be reduced by more waste. This is done by obstructing the filters, which prevents them from effectively circulating the water, and encouraging algae development, which at night consumes oxygen. It’s also crucial to remember that bacteria cannot break down waste without oxygen. The more oxygen is consumed in this process the more rubbish you have in your tank.

Related Post: How Many Mollies Should Be Kept Together?

3. The Molly in Your Tank Isn’t Happy

Due to a lack of oxygen, mollies will occasionally run to the top and remain there. However, people frequently do this to flee the unfavorable circumstances below, which include:

  • High Toxin Concentration: Ammonia, nitrates, and nitrites are frequently drawn to fish tanks by the presence of fish. Ammonia is the most hazardous of the three. Ammonia may injure your fish with just a trace quantity. The mollies will finally perish at a greater concentration. However, they will have trouble breathing before that happens. The gills are inflamed, as you can see if you look at them closely. They will also start to gasp for air, which often indicates that there is not enough oxygen in the tank. However, you must take into account the ammonia levels if you have examined your tank and the oxygen levels are sufficient. Mollies will flee the ammonia by running to the surface. Until the scenario below is handled, they will remain at the top. Mollies are marketed as hardy fish that can endure a variety of circumstances. To grow, they require particular water characteristics, though. Temperature and pH are included in it. While they can initially put up with the incorrect settings, ultimately they will find the pain intolerable. Your mollies may react by swimming at the top if you unintentionally subjected them to the incorrect pH or temperature. Remember that hardness is the most problematic of these characteristics. Soft water irritates mollies.
  • Size: Mollies are gregarious fish who require freedom. They will seek respite at the top if you force them to live in a small, overcrowded tank, although this isn’t always effective. Because of this, aquarists prefer to raise mollies in wide tanks as opposed to tall ones.

4. The Fish are Starving

Because they are constantly fed from the top of the tank, certain fish congregate there when they are hungry. The mollies in this area of the tank have only acclimated to your routine if you only visit them around mealtimes.

Mollies are aware of when to eat. If you notice them at the top at other times of the day, they are undoubtedly starving and are hanging out there in the hopes of getting food. After meals, they often swim back to the lower areas.

5. Your Molly is Anxious

Fish may behave in ways that are not entirely normal when under stress. That involves either remaining at the top or remaining motionless at the bottom of the tank. There are several things that might cause stress, such as low water levels, bullying, harsh lighting, underfeeding or overfeeding, a lack of vegetation, human traffic around the aquarium, etc.

Molly Aggression

6. A Disease is Present in the Fish

An infection or sickness can alter mollies’ behavior, much like stress might. When parasites have infected their gills, some of them may become sluggish while others will search for respite above the surface.

If such is so, your molly will exhibit signs like gasping and laborious breathing that is typical of oxygen-deficient tanks. You could even observe that the gills have changed shape and don’t appear to be in good health.

A Disease is Present in the Fish

How to Handle Mollies that always Swim at the Top?

While some mollies may choose to remain at the top, this isn’t typical behavior, and you may use the strategies listed below to deal with it:

1. Adding Oxygen to Your Tank

The oxygen levels in an aquarium may be raised by a number of methods, including:

  • Water Change: Your aquarium will benefit immediately from a significant water change, therefore that should be your initial move. The water change will result in new water being added to the tank, which will raise the oxygen levels. Powerheads, air stones, and agitation filters should be installed first. If you already have a filter, consider upgrading to a more trustworthy type. If your tank is too huge, you might consider adding several filters. The usage of these technologies will increase the aquarium’s oxygen intake and distribution.
  • Temperature: If your tank is hot, turn off the heater and turn off the lights. Keep it turned off until the tank temperature drops significantly. If the water is still too hot, blow air over the tank’s surface with a fan.
  • Temperature: If your tank is overheated, turn off the lights and turn off the heater. Turn it off until the temperature in the tank has dropped sufficiently. If the water is still too hot, blow it across the tank’s surface using a fan. In an emergency, don’t be afraid to add a few ice cubes (in zip-close bags) to the water. I also recommend having a thermometer on hand. You don’t want to drop the temperature so low that the water is too chilly for your mollies.
  • Maintenance: Make every effort to maintain the tank clean. Periodically vacuum the substrate. It is imperative that you get rid of any leftovers and dead organisms you detect. Ammonia and other poisons will rise if the garbage in the water is allowed to build up.
  • Plants: By adding more plants, you may raise the oxygen levels in the tank. But first, make sure there is enough illumination in the tank. If not, plants will use oxygen instead of producing it.

2. Molly Water Modification

Molly aquariums require frequent water changes. Only in this manner can the concentration of toxins such as ammonia be regulated. However, water changes alone are insufficient. A good filter is required to cleanse the water of particulates.

Unsuitable Water Chemistry

As previously stated, the substrate should be vacuumed, and all dead plants and animals should be removed. Test the pH (7.5 to 8.5), temperature (75 to 80 degrees F), and hardness (12 to 25 dGH, 10-25 dkH) frequently to ensure they remain within the ideal range.

Also, at all costs, avoid overstocking and overcrowding. Each inch of an adult fish consumes one gallon of water in an average aquarium.

3. Taking Care of Swim Bladder Illness

If the aquarium offered a favorable atmosphere for treating swim bladder illness, it would be beneficial. The problem may worsen if improper settings are used. Because they impair digestion, low temperatures are particularly harmful.

Swimming Bladder Illness

The mollies should go on a 48-hour fast once the tank conditions have been improved. They will have more time to digest the food already in their systems as a result. Use cooked, peeled peas to help with constipation after the fast. Maintain this food for three days with the mollies.

4. Stress Reduction

By making the tank feel welcoming, you may reduce stress. That entails introducing decorations and vegetation that mollies may hide behind, getting rid of bullies, and removing anything that can frighten the fish, such as string lights.

5. Giving Fish the Right Food

A molly that is remaining at the top shouldn’t be dealt with by feeding it. Feeding Mollies should occur twice daily. They should also be given food that they can consume in two to three minutes. After that time, if you still see leftovers, your fish have received too much food.

Don’t feed your molly again just because it is hanging out at the top if you have already fed it and are certain the amounts you supplied were adequate. Mollies will continue to eat if you continue to feed them, just like other fish do. This explains why overeating is so widespread.

The Bottom Line on Why Do Molly Fish Stay At The Top Of The Tank? 

Constipation and a swim bladder illness should be among your first thoughts if your molly frequently swims in the upper portions of the tank. You may also see strange swimming habits, including irregular swimming, with this disease. You should examine the water’s pH, temperature, ammonia, nitrates, and nitrites while addressing that situation. A test kit makes it simple to accomplish that. Increase the frequency of water changes and thoroughly clean the tank if one of the parameters is off.

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