How To Get Rid of White Cotton Like Stuff in Fish Tank

Did you know the white cotton like stuff in your fish tank is actually fungus?

If gone untreated the fungus will spread and will create white cotton like suff and white fuzzy balls in your fish tank.

If you want to know, how to get rid of the white fungus from your aquarium continue reading.

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What Is The White Cotton Like Stuff In My Fish Tank

The white cotton like stuff in your fish tank is a type of fungus growth and will appear as white fuzzy stuff, white fuzzy balls or floating white stringy material.

The white fungus is highly contagious and will grow and spread in your tank quickly if left untreated. It can also cause harm to your fish.

How To Get Rid of White Cotton Like Stuff In Fish Tank

The white cotton like stuff is fungus that is growing in your fish tank.  To get rid of it you need to treat the water and then identify the root cause to prevent the fungus from coming back.

In the picture below is what the white stuff will look like in your fish tank.

White Cotton Stuff In Tank

To remove the fungus follow these steps:

1. Remove Fish From Fish Tank

Before treating the aquarium water for fungus it is important to remove your fish from the tank. Place some aquarium water in a separate fish tank or bucket then transfer your fish to it.

2. Add Aquarium Salt (Optional Step)

Aquarium salt is a good treatment for your fish to help them to recover from any fungus, mold or algae that they might have on them or in them.

Simply add the salt to the water the fish are in, make sure to read the instructions on how much salt to add to the water.

3. Remove & Clean Aquarium Decorations

Now we need to remove any aquarium decorations such as aquarium rocks, statues, plastic plants that have the white fungus on them and give them a good clean.

It is important that you remove all the white fungus from the decorations as the fungus will grow back even if there is the smallest bit left.

I recommend to bin any decorations that are hard to clean as you might have trouble to remove all the fungus from the decoration.

To clean the decorations follow these steps

  • Remove the ornament from the tank.
  • Run it under hot water for 5 minutes.
  • Make sure to rinse all of the decoration, use a brush to remove larger white fuzzy stuff.
  • Fill a bucket with hot water and add an aquarium water treatment kit.
  • Wait for 1 hour.
  • Remove the ornament and rinse again with hot water.
  • Put back in to aquarium.

The same method above can be applied if you have white stuff on driftwood in your tank.

Treat White Fuzzy Stuff On Aquarium decoration

4. Remove Aquarium Plants

I recommend to remove all plants from your fish tank and throw them away. Fungus and mold can be very hard to remove from plants, Fish will eat plants and in turn can also eat the fungus or mold and can cause your fish to become ill.

Remove any plants from your fish tank that are showing signs of fungus or mold grough as soon as you can. The early signs of fungus on the plants include the leaf edges looking hazed and worn out, after that white fuzzy fungus will start to grow as shown in the below picture.

Once the plants have been removed you can clean them using the following instructions

  1. Place in to a small tank with no fish.
  2. Apply an aquarium water treatment kit.
  3. Raise the temperature of the aquarium (This will help to kill the fungus and bacteria).
  4. Wait a few days.
  5. Add some aquarium salt to the tank.
  6. Wait a few days.
  7. Make sure the water is clear and not white fuzzy looking.
  8. Place the plant back to the original tank.

White Fungus On Aquarium Plants

5. Treat Water With Water Conditioner

Now using an aquarium water conditioner such as Aquacare, treat the aquarium water following the instructions carefully. Make sure to leave enough time before adding your fish back in to the fish tank.

The white algae will now start to be killed in your fish tank. Any white fuzzy balls or lose white fluff can be removed with a fish net at this time.

Make sure to leave enough time for the water conditioner to work and check that there is no white fungus left in the tank before putting your fish back in.

The following are signs of white fungus

  • Cloudy or milky water
  • White or grayish film covering surfaces, such as glass, rocks, or decorations
  • Reduced visibility due to algae growth
  • Slime or stringy texture in the water
  • Increased nitrate or phosphate levels in the water

6. Test Fish Tank Water Quality (Optional)

I recommend to test the aquariums water to make sure that the treatment has worked. The result will identify if we were successful in removing the white fungus or not.

To test fish tank water, you can use a water testing kit specifically designed for aquariums. These kits usually include test strips or liquid reagents for measuring parameters like pH, ammonia, nitrite, nitrate, and sometimes other parameters like hardness and alkalinity.

  • pH: Depending on the type of fish, pH levels can vary, but a range of 6.5 to 7.5 is suitable for most freshwater fish.
  • Ammonia: Ammonia should be undetectable or at very low levels (ideally 0 ppm) since it is toxic to fish.
  • Nitrite: Nitrite levels should also be undetectable or very low (ideally 0 ppm). Elevated nitrite levels can be harmful to fish.
  • Temperature: Different species have specific temperature requirements, but generally, a range of 75-82°F (24-28°C) is suitable for most tropical freshwater fish.

Preventing White Fungus In Your Fish Tank

If you are worried about the growth of white fungus in your fish tank there are a few things you can do regularly to prevent a fungus invasion.

These tasks include

Quarantine Infected Fish

Separate any fish showing signs of the white fungus into a quarantine tank to prevent spreading the infection to healthy fish. If you do not know what the signs are of fungus on your fish take a look at the next section.

Improve Water Quality

Ensure optimal water conditions by maintaining appropriate temperature, pH levels, and ammonia/nitrite/nitrate levels. Regular water changes and good quality filtration maintenance are essential.

Clean and Disinfect Equipment

Clean and disinfect any equipment or decorations that have come into contact with infected fish or affected areas. This helps prevent cross-contamination.  You should also clean all decorations every 2-4 weeks

Reduce Stress

Minimize stress factors for your fish, such as overcrowding, sudden changes in water parameters, or poor nutrition. Stressed fish are more susceptible to infections.

Maintain Good Hygiene

Practice good aquarium hygiene by regularly cleaning and vacuuming the substrate, removing excess organic matter, and keeping the tank clean.

Don’t Over Feed Fish

The food that is not eaten will stay in your tank and will turn in to harmful bacteria which could then start a fungus growth in your tank.

What Is the White Stuff on My Fish

The white fuzzy stuff that you are noticing on your fish is most likely a fungus that is growing on its skin, most likely white spot disease or ich.

If you don’t act soon, it may affect your fish’s health. Do not beat yourself up about it because fungal spores are naturally producing in many fish tanks.

If you think your fish might have white spot disease or ich look for these signs

  • White spots: Small, white dots that resemble grains of salt on the fish’s body, fins, or gills.
  • Scratching or rubbing: Infected fish may exhibit increased scratching or rubbing against tank surfaces or objects.
  • Behavior changes: Fish may become more restless or exhibit erratic swimming patterns.
  • Rapid breathing: Infected fish may show increased respiratory rate or gasping at the water surface.
  • Loss of appetite: Infected fish may refuse food or exhibit a decreased interest in eating.
  • Lethargy: Fish may appear sluggish or inactive.
  • Clamped fins: The fish’s fins may be held close to the body instead of being spread out.
  • Pale or faded coloration: Infected fish may show a loss of vibrancy or a pale appearance.
  • Discomfort: Fish may display signs of distress, such as flashing (sudden darting movements) or hiding.
YouTube video

Treating White Fungus In Fish

If your fish have white fungus on them they they have either white spot disease or ich.  Below is how you would treat this condition.

  • Seperate The Infected Fish: Remove the infected fish and place them in another tank until they have been fully treated.
  • Increase temperature: Gradually raise the aquarium temperature to around 86°F (30°C) for tropical fish or follow the specific recommendations for your fish species. Higher temperatures accelerate the life cycle of the parasite, making it more vulnerable to treatment.
  • Medications: Use a suitable ich medication or treatment as directed by the product instructions. Common medications include those containing malachite green, formalin, or copper. Follow the dosage and duration recommendations carefully.
  • Remove carbon filtration: If you have a carbon filter, remove it during the treatment period, as carbon can absorb the medication and reduce its effectiveness.
  • Treat the entire tank: Ich is contagious, so treat the entire aquarium, even if only a few fish show signs of infection. Treatments typically involve adding the medication directly to the water.
  • Monitor and repeat treatment: Observe the fish closely during and after treatment. If necessary, repeat the treatment according to the recommended intervals until all signs of white spots have disappeared.
  • Water changes: Perform partial water changes (about 25%) after completing the treatment to remove any remaining medication or toxins. Ensure the water parameters are within the appropriate range for your fish species.
  • Address underlying issues: Assess and address any underlying causes of stress, such as poor water quality, tank population, overcrowding, or improper nutrition. Maintaining optimal conditions will help prevent future outbreaks.

What Causes The Growth Of White Fungus

The main reasons white fungus has invaded your fish tank are poor water quality, Over feeding, To much sunlight exposure.

It is important to spot the root cause of the fungus growth as soon as you can to prevent a fungus explosion within your fish tank.

You should check the following items to prevent a fungus invasion.

  • Poor water quality: High levels of organic waste, such as uneaten food or decaying plant matter, can contribute to the growth of fungus.
  • Imbalanced water parameters: Fluctuations or imbalances in water parameters, such as pH, temperature, or hardness, can create conditions favorable for fungal growth.
  • Stress and weakened immune system: Fish that are stressed due to factors like poor water conditions, overcrowding, inadequate nutrition, or sudden changes in environment are more susceptible to fungal infections.
  • Overfeeding fish: The left over food will rot and will eventually grow in to fungus if not removed from the tank.
  • Contamination: Introduction of contaminated water, plants, or equipment into the aquarium can introduce fungal spores.
  • Inadequate filtration and oxygenation: Inadequate filtration can lead to a buildup of organic matter and stagnant water, providing an environment suitable for fungal growth. Insufficient oxygenation can also contribute to the growth of fungi.
  • Introduction of infected fish or plants: Adding new fish or plants without proper quarantine or inspection can introduce fungal infections into the aquarium.
  • Sunlight exposure: Try not to place your fish tank in a position where it will be in direct sunlight for most of the day.

overfeeding fish


Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.