Why Is My Molly Fish Floating At The Top? (3 Easy Solutions)

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I won’t forget the feeling I got when I saw my molly fish floating at the top of the tank. It was still alive, but it floated in an odd position and breathed heavily.

At first, I had no idea what was going on or what to do. I was sure that I was about to lose my fish. However, some research online saved my molly fish’s life.

In this article, I will show you what causes mollies to float at the top of the tank, how to fix that issue, and how to prevent it from happening again in the future.

Let’s get started.

Why Is My Molly Fish Floating at the Top?

Your molly fish is most likely floating at the top due to swim bladder disorder, which affects its buoyancy control.

This condition may be caused by various reasons, which I’ll explore below. Here’s how these factors contribute to the condition in your molly fish:

  • Overeating: Molly fish that are overfed can develop swim bladder issues. Overeating may cause the swim bladder to be physically compressed, hindering its proper functioning.
  • Poor water quality: When molly fish live in polluted water, they may suffer swim bladder disorder. High levels of toxins can lead to infection or inflammation of the swim bladder.
  • Abrupt changes in water temperature: Molly fish are sensitive to sudden temperature shifts, which can stress their system and potentially affect their swim bladder.
  • Bacterial infections: Certain bacteria can invade the swim bladder of molly fish. This could result in inflammation, disrupting the fish’s ability to regulate buoyancy.
  • Genetics: Some molly fish are genetically predisposed to swim bladder issues. It’s not the most common reason, but it does account for a small percentage of cases.
  • Ingesting air: If your molly fish swallows too much air while feeding at the water surface, it could disrupt their swim bladder’s operation.

Also Read: Molly Fish Swim Bladder Disease

What Should I Do if My Molly Fish Floats at the Top?

If your molly fish floats at the top, it’s likely suffering from swim bladder disorder, and you need to take the following steps to treat the condition:

  • Dietary changes: Overfeeding can cause the disorder, so reduce your molly fish’s food intake by 30%. Incorporate a mix of high fiber foods like daphnia, which aids digestion.
  • Temperature adjustment: Molly fish thrive in stable temperatures. Maintain your tank at a consistent 75°F (±2°F) to alleviate the fish’s stress and assist swim bladder function.
  • Isolation: Place the affected molly fish in a quarantine tank. A 5-gallon tank is ideal for this purpose, preventing the potential spread of bacterial infections.
  • Water quality improvement: Perform regular water changes, replacing 25% of the tank water weekly. This ensures a clean, low-toxin environment for your molly fish.
  • Antibiotics: If a bacterial infection is suspected, consider antibiotics like kanamycin, usually dosed at 8-10 mg per liter of tank water, under the guidance of a vet.
  • Fasting: Implement a 48-hour fast for your molly fish. This break in feeding helps resolve digestive blockages that might cause swim bladder issues.
  • Pea feeding: Post fasting, feed your molly fish a pea meal. One cooked, shelled pea (chopped finely) aids digestion and alleviates pressure on the swim bladder.
  • Consult a vet: If symptoms persist after these steps, consult an aquatic veterinarian. Early intervention can significantly improve the recovery rate.
  • Commercial Products: In the meantime, you can apply commercial products available online to fight infections. My suggestion: API MELAFIX (link to Amazon).

How Can I Prevent Swim Bladder Disorder in Molly Fish?

To prevent swim bladder disorder in your molly fish, you need to maintain good tank conditions and feeding practices:

  • Balanced diet: Feed your molly fish a balanced diet with a 70:30 ratio of protein to fiber. This mix supports healthy digestion and swim bladder function.
  • Proper feeding methods: Feed molly fish mid-water to prevent them from ingesting air. An auto-feeder can dispense food at set intervals and locations, reducing surface feeding. My recommendation: Petbank Automatic Fish Feeder (link to Amazon).
  • Regular water changes: Commit to weekly water changes, replacing 25% to maintain water quality.
  • Stable water temperature: Keep your tank’s temperature at a stable 75°F (±2°F). A tank heater with a thermostat can help maintain this optimal temperature for molly fish.
  • Adequate tank space: Provide at least 4-5 gallons of space per molly fish. Overcrowding can cause stress and illness, increasing the risk of swim bladder disorder.
  • Routine check-ups: Conduct weekly health check-ups. Early detection and treatment of swim bladder disorder can increase the survival rate of affected molly fish by up to 75%.

What Is the Prognosis of Swim Bladder Disease in Molly Fish?

The prognosis of swim bladder disease in molly fish varies greatly depending on the cause and how quickly treatment is started.

If diagnosed early and managed effectively, molly fish can recover completely, but delay in treatment or severe cases could lead to chronic issues or even mortality.

What Are Some Less Common Reasons for Molly Fish Floating?

As I mentioned earlier, swim bladder disorder is the most common reason behind a molly fish that floats at the top. However, some less common reasons are also possible:

1. Your Molly Fish Died

It’s sad but possible that a floating molly fish could be deceased. In death, a fish’s body may float due to gases produced during decomposition:

  • Post-mortem bloating: Gases accumulate in a deceased molly fish’s body, causing it to float. This usually happens several hours after death.
  • Lack of movement: Unlike a living fish with swim bladder disorder, a dead molly fish will not attempt to change its position or swim around in the tank.
  • Physical changes: Dead molly fish often exhibit physical signs such as color fading, cloudy eyes, or damaged fins, which distinguish them from live fish with health issues.

Also Read: Why Is My Molly Swimming Upside Down?

2. Your Molly Fish is Looking for Food

Molly fish may occasionally float near the surface in anticipation of feeding, which is often misinterpreted as a sign of illness:

  • Feeding habits: If your molly fish is conditioned to receive food at the surface, it may float there when hungry, waiting for the food to be dropped.
  • Attention-seeking behavior: Molly fish are intelligent and may float at the top to get your attention, especially if they associate your presence with feeding time.
  • Regular feeding times: Molly fish fed on a strict schedule may start to float at the top around their usual feeding times, in anticipation of their meal.


For those of you who are short on time, here is a brief overview of what I discussed earlier:

  • Swim bladder disorder in molly fish can be caused by overeating, poor water quality, temperature changes, infections, genetics, or air ingestion.
  • Treating swim bladder disorder involves dietary changes, temperature adjustment, isolation, water quality improvement, antibiotics if needed, fasting, pea feeding, and vet consultation.
  • Preventing swim bladder disorder requires a balanced diet, proper feeding, regular water changes, stable temperature, adequate tank space, and health check-ups.
  • The prognosis varies based on the cause and prompt treatment. Early intervention improves recovery, while delay or severity can lead to chronic issues or mortality.
  • Floating molly fish may indicate death or hunger, as they may anticipate feeding or seek attention near the surface.