Why Is My Molly Fish Blowing Bubbles? (5 Quick Solutions)

Disclosure: When you purchase something through my affiliate links, I earn a small commission. As an Amazon Associate, I earn from qualifying purchases.

A few years ago, I caught my molly fish blowing bubbles consistently. At first, I thought that this was a normal behavior that could be ignored.

However, as the days passed, my fish’s state got worse, and I was sure that I was about to lose it. That was when I began researching and learned what to do.

In this article, I will explain what causes molly fish to blow bubbles in a consistent manner, how to treat it, and how to keep it from happening again in the future.

Let’s get started.

Why Does My Molly Fish Produce Bubbles?

Here are some common causes behind a molly fish that consistently blow bubbles:

1. Insufficient Oxygen Levels

Molly fish need a consistent oxygen level in their environment to breathe and function properly.

When oxygen levels are low, your molly fish might produce bubbles as a stress response. Here is what you should know:

  • Oxygen Level Impact: Low oxygen can lead to hypoxia in molly fish, leading to increased breathing effort and bubble production.
  • Dissolved Oxygen Demand: Molly fish require a dissolved oxygen concentration of 5-6 mg/L; anything less might result in bubble production.
  • Overcrowding Consequences: An overcrowded tank can reduce available oxygen, potentially causing bubble production in molly fish.
  • Absence of Aeration: Lack of proper aeration can reduce oxygen levels, leading to possible bubble production in molly fish.
  • Oxygen-depleting Elements: High amounts of algae or uneaten food can lower oxygen levels, potentially causing molly fish to produce bubbles.

Also Read: Why Is My Molly Fish Breathing Fast?

2. Poor Water Quality

Poor water quality can cause your molly fish to produce bubbles. They are sensitive to changes in their environment, particularly harmful substances in the water.

Let’s delve into that:

  • Toxic Compound Effects: High levels of ammonia, nitrites, or nitrates can trigger stress in molly fish, leading to bubble production.
  • Chemical Exposure Stress: Molly fish exposed to harmful chemicals, such as chlorine, might produce bubbles due to stress.
  • Infrequent Water Changes: Failing to change aquarium water regularly can cause harmful substance buildup, potentially leading to bubble production in molly fish.
  • Lack of Water Conditioner Use: Without a water conditioner to neutralize harmful substances, molly fish might react by producing bubbles.
  • Incorrect pH Levels: pH levels outside the 7.0-8.2 range can cause stress in molly fish, potentially leading to bubble production.

3. Elevated Temperature

Molly fish thrive at temperatures between 75 and 80 degrees Fahrenheit. Temperatures beyond this range might cause your molly fish to produce bubbles.

Let’s explore this further:

  • Oxygen and Temperature Interplay: Higher water temperatures reduce its capacity to hold oxygen, potentially causing bubble production in molly fish.
  • Effects of Temperature Fluctuations: Rapid or significant temperature changes can cause stress in molly fish, leading to bubble production.
  • Overuse of Aquarium Heater: Incorrect use of the aquarium heater can cause temperature spikes, prompting molly fish to produce bubbles.
  • Aquarium Placement Factors: A sunny or overly warm spot can raise the water temperature, causing molly fish to produce bubbles.
  • Summer Heat Impact: Naturally higher temperatures in the summer can lead to increased water temperature, causing molly fish to produce bubbles.

4. The Issue of Gas Bubble Disease

Gas Bubble Disease, or GBD, can make molly fish produce bubbles. This problem arises when the fish come into contact with water that is supersaturated with gases.

Here’s what can contribute to this phenomenon:

  • Manifestation of GBD: The creation of bubbles, pop-eye symptoms, and bloating are all indications of GBD in molly fish.
  • Triggering GBD: Swift changes in either pressure or temperature can lead to gas supersaturation, causing GBD and consequently bubble formation in molly fish.
  • Mismanagement of Aerator and Filter: If aerators and filters aren’t used properly, they can lead to gas supersaturation, which can give rise to GBD in molly fish.
  • Abrupt Pressure Changes: Sudden shifts in pressure can result in gas supersaturation, a key contributor to GBD and bubble formation in molly fish.
  • Environmental Elements: Different factors within the fish tank can lead to gas supersaturation, potentially causing bubbles to form in molly fish.

5. Stress

High levels of stress can trigger bubble formation in your molly fish. A range of factors can contribute to stress, from unsuitable tank companions to poor water quality.

Take these into account:

  • Unsuitable Tank Companions: Keeping molly fish with hostile or incompatible species can cause stress, which may result in bubble formation.
  • Limited Space: A cramped tank can cause stress, potentially triggering bubble formation in molly fish.
  • Feeding Concerns: A poor diet or erratic feeding schedules can stress out molly fish, possibly causing them to produce bubbles.
  • Abrupt Environmental Shifts: Quick changes in the water conditions or the environment can stress molly fish, potentially leading to the production of bubbles.
  • Noise and Light Sensitivity: High noise levels or intense light can cause stress in molly fish, potentially triggering bubble formation.

Also Read: Stress In Molly Fish

How to Treat Molly Fish That Continuously Produce Bubbles

Fortunately, there are some practical steps you can take to treat your molly fish:

1. Improve Oxygenation

Oxygen is critical for molly fish, and insufficient levels can trigger unusual behavior like excessive bubble production.

By enhancing oxygenation, the health of your molly fish can significantly improve. To accomplish this:

  • Install Air Stones: Air stones create surface agitation, enhancing gas exchange. Aim for at least one standard-sized air stone for every 10 gallons of tank water. My recommendation: Hygger Aquarium Air Stone (link to Amazon).
  • Incorporate Live Plants: Live plants like anubias or java fern generate oxygen during daylight hours. Try to maintain around 30% of the tank floor covered with live plants.
  • Maintain Appropriate Stocking Levels: Overstocking reduces available oxygen. Stick to the general guideline of one molly fish per 3-5 gallons of water.
  • Perform Regular Water Changes: Replace 25-30% of the tank water weekly; fresh water has higher dissolved oxygen. For a 20-gallon tank, this would be 5-6 gallons weekly.
  • Utilize Air Pumps: Air pumps are particularly beneficial in larger tanks. Choose one rated for the size of your tank, e.g., a 40-gallon pump for a 40-gallon tank.

Also Read: Do Molly Fish Need An Air Pump?

2. Maintain Water Quality

Water quality directly affects the health of molly fish. A poorly maintained environment can cause problems, including constant bubble production.

For proper water quality:

  • Adopt Routine Cleaning: Clean the tank weekly to prevent waste buildup. This includes vacuuming about 30% of the substrate each week in a 20-gallon tank.
  • Regularly Test Water: Using testing kits, monitor the pH, ammonia, nitrite, and nitrate. Molly fish thrive with a pH between 7.5-8.5, ammonia and nitrite at 0ppm, and nitrate below 20ppm. My recommendation: API FRESHWATER MASTER TEST (link to Amazon).
  • Control Feeding: Overfeeding leads to excess waste, negatively impacting water quality. Feed your molly fish once or twice a day, only as much as they can eat in 2-3 minutes.
  • Implement Biological Filtration: It helps maintain water quality by breaking down harmful waste into less harmful substances. A filter rated for your tank size can maintain a healthy bacteria colony. My recommendation: Fluval C4 Power Filter (link to Amazon).
  • Change Water Regularly: Replace 20-25% of the tank water weekly to remove toxins and replenish minerals. For instance, replace 5 gallons weekly in a 20-gallon tank.

Also Read: Molly Fish Tank Setup

3. Regulate Temperature

Molly fish require a consistent temperature to maintain good health. Fluctuations or extreme temperatures can lead to stress and unusual behaviors.

Here’s how to regulate it:

  • Use Heaters: Heaters maintain consistent temperature. Molly fish prefer 72-78°F (22-26°C), so choose a heater capable of maintaining this range for your tank size. My recommendation: Orlushy Submersible Aquarium Heater (link to Amazon).
  • Install a Thermometer: It ensures the temperature remains in the safe range. Monitor daily to catch potential problems early.
  • Avoid Rapid Temperature Changes: Sudden shifts can stress molly fish. When changing water, ensure new water is within 1-2°F of the tank water.
  • Provide Insulation: An insulated tank can resist temperature fluctuations from the room. For example, a foam mat under the tank can provide extra insulation.
  • Control Lighting: Excessive lighting can raise water temperature. Limit artificial light to about 8-10 hours a day to mimic a natural day-night cycle.

Also Read: Molly Fish Temperature

4. Treat Gas Bubble Disease

Gas bubble disease can cause molly fish to produce bubbles. It occurs due to supersaturated gases in water, which forms bubbles in fish tissues.

To treat it:

  • Consult a Vet: They can diagnose the condition and suggest a treatment plan, which usually includes changes in water quality and possibly medication.
  • Perform Emergency Water Changes: Replace 50% of the tank water immediately if you suspect gas bubble disease. Ensure the new water matches the old water’s temperature and conditions.
  • Use Anti-Gas Bubble Disease Products: There are over-the-counter treatments available, which can be dosed according to the product’s instructions.
  • Lower Water Temperature: Higher temperatures can hold less dissolved gases, increasing the risk of this disease. Lower the water temperature within the safe range for molly fish (72-78°F).

Also Read: 15 Molly Fish Diseases & Their Treatments

5. Minimize Stress

Stress can cause a range of health problems in molly fish, including bubble production. By minimizing stress, your molly fish will be healthier and happier.

These steps can help:

  • Provide Sufficient Room: Overcrowded environments can cause stress in fish. To ensure ample space, it is recommended to have a tank capacity of at least 20 gallons for a small community of molly fish.
  • Provide Hiding Places: Use plants, rocks, or aquarium decorations to create hiding spots. Aim for 3-4 hiding spots in a 20-gallon tank.
  • Ensure Balanced Diet: A varied diet keeps molly fish healthy and stress-free. Offer a mix of flakes, live, frozen, and vegetable foods.
  • Maintain a Stable Environment: Frequent changes in water conditions or temperature can cause stress. Strive for consistency in pH, temperature, and other water conditions.
  • Avoid Aggressive Tank Mates: Peaceful species are best suited for cohabiting with molly fish. Avoid aggressive fish like cichlids or large barbs.

Here are some peaceful species that can be kept with mollies:

  • Platies (Xiphophorus maculatus)
  • Guppies (Poecilia reticulata)
  • Swordtails (Xiphophorus helleri)
  • Corydoras Catfish (Corydoras spp.)
  • Cherry Barbs (Puntius titteya)
  • Zebra Danios (Danio rerio)
  • Harlequin Rasboras (Trigonostigma heteromorpha)

On the other hand, here are aggressive species that shouldn’t be mixed with mollies:

  • Tiger Barbs (Puntigrus tetrazona)
  • Convict Cichlids (Amatitlania nigrofasciata)
  • Red-Tailed Black Shark (Epalzeorhynchos bicolor)
  • Green Terror Cichlid (Andinoacara rivulatus)
  • Jack Dempsey Cichlid (Rocio octofasciata)
  • African Cichlids (Various species, such as Melanochromis auratus)
  • Siamese Fighting Fish (Betta splendens)

Also Read: 19 Great Neon Tetra Tank Mates

Preventive Measures to Avoid Bubble Production in Molly Fish in the Future

Prevention is the best approach to avoid bubble production in molly fish. Proactive care and regular monitoring of their environment are key:

  • Maintain Optimal Water Parameters: Ensure stable water conditions for molly fish by managing temperature and pH: 72-78°F (22-26°C) and 7.5-8.5 respectively.
  • Implement Regular Cleaning: Follow a weekly cleaning routine, which includes vacuuming the substrate and changing about 25% of the tank water.
  • Control Diet: Feed molly fish only what they can consume in 2-3 minutes, once or twice a day, to avoid overfeeding.
  • Provide Adequate Oxygenation: Utilize air stones and live plants, and maintain a stocking ratio of one molly fish per 3-5 gallons of water for optimal oxygenation.
  • Monitor Fish Behavior: Observe your molly fish daily for any signs of stress or disease for early detection and effective treatment.

Also Read: Why Is My Molly Hiding?


For those of you in a rush, here is a quick overview of what I discussed above:

  • Molly fish may produce bubbles due to factors such as low oxygen levels, poor water quality, elevated temperatures, gas bubble disease, and stress.
  • To address bubble production, improving oxygenation, maintaining water quality, regulating temperature, treating gas bubble disease, and minimizing stress are essential.
  • Practical steps to treat molly fish include enhancing oxygenation through air stones and live plants, maintaining water quality through cleaning and filtration, regulating temperature with heaters, treating gas bubble disease under veterinary guidance, and minimizing stress through adequate space and balanced diet.
  • Choosing compatible tank mates and following proper feeding and environmental practices can help prevent bubble production in molly fish.
  • Regular monitoring of water parameters, proactive care, and early detection of stress or disease are crucial for ensuring the well-being of molly fish and preventing bubble production.