What is White Cotton Like Stuff in Fish Tank?

Are you noticing white cotton like stuff in your fish tank that looks unhealthy for your fish?

Can this white cotton / fuzz in fish tank harm your fish? Do you want to know what the best way is to get rid of this white cotton like stuff?

Most people think this is white algae in the fish tank but it is not, so what is it?

What is White Cotton Like Stuff in Fish Tank?

The white cotton stuff in your fish tank is either bad bacteria or fungus.  Most people mistake this for white algae.

The best way to treat this infection is by using a aquarium water treatment kit (Available On Amazon)

The white cotton fuzz / stuff will look something like in the video below

YouTube video

Let’s first know about the causes and symptoms of the white stringy stuff in your fish tank, So that you can treat your aquarium accordingly and restore a healthy environment for your fish.

What Is the White Fuzzy 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. 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.

Unfortunately these fuzzy white things that appear harmless can cause fish to become stressed or sick. The fungus looks like white cotton or wool that grows on your fish predominantly in these areas:

  • skin
  • fins
  • gills
  • mouth

Aquarium first aid salts may help in the tank, but make sure to follow the instructions on the product you choose. Continue to test your tank’s water to make sure that the parameters are ideal.

What Are the White Fuzzy Balls in My Fish Tank?

The white fuzzy balls you are noticing in your fish tank are probably not fish eggs. They may have arrived due to three different factors:

  • Algae
  • Fungus
  • Bacteria

When fungus or bacteria builds up and if you don’t address this problem, you will end up with mold that could turn brown or black. Sometimes it may look like fuzzy white balls instead.

It is hard to diagnose the fuzzy white balls in your tank without taking a closer look at water parameters and the state of your aquatic life in the tank.

Look closely for fin rot, algae growth and change the water more regularly. The waste that your fish produces can end up becoming food for the fuzzy white balls and it may cause them to spread.

It can also be bacteria related gunk that accumulates near the substrate. The best way to tell the difference between these fuzzy white balls being fungus or bacteria and not fish eggs is if they are spread apart because fish eggs are clumped together.

What Causes The Growth Of White Cotton Stuff?

White cotton stuff does not start to appear for no reason, The main reason for white fluffy stuff in your fish tank is the presence of fungus and parasites.

There are few reasons behind that allow the growth of these fungus and parasites inside the aquarium. Further more, these will infect the fish as well and will make them unwell. T

he common causes behind the growth of these moulds are

  • Buying of the fish suffering from fin rot or bacterial infection
  • Overfeeding of fish and leftover allows the growth of fungus, bacteria or algae over it.
  • Dirty tank means you didn’t change the water and the waste of fish becomes food for fungus or some other parasite.
  • The water temperature is not controlled.

overfeeding fish

Signs Of White Cotton Stuff In Aquarium?

Apart from the obvious signs of white fuzzy stuff / white stringy stuff in your aquarium where are other signs you can look out for which include

  • White spots on the fish fin or tail
  • White cotton attached to the pebbles and pool decoration
  • Presence on the surface and walls of the tank
  • White cloudy look in fish tank
  • White fuzzy stuff growing on ornaments in tank (As shown below)
  • White fluff floating in fish tank
  • Aquarium driftwood has white fuzz on it

white fluffy stuff in fish tank

When you see the water is not clear and looks white and cloudy and the glass of tank has a fluffy white layer, it means it is time to maintain your tank and prevent the fish from getting diseases.

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

Once you find the sign of infection in the tank, you should apply the treatment as soon as you can. Otherwise, you may lose some of your fish to diseases. The treatment depends on the level of the disease.

To get rid of white cotton stuff in your fish tank follow these steps

  1. The first thing you will need to do is treat the water with something like an aquarium water treatment kit (Available On Amazon)
  2. Use salt bath technique for the fish
  3. It is the standard method to treat the fish as well as a tank with parasitic infection you can do it by yourself. The steps for treating fish with this method are
  4. Take four tablespoons of salt in the bucket or separate tank.
  5. Add the water from the tank to make the level of one gallon
  6. Mix the salt thoroughly, place the fish from the container in the bucket.
  7. Keep it inside for five to thirty minutes depending on severity level.

White Cotton Stuff In Tank

Point to Consider

  • Observe the behavior of fish properly throughout treatment. If you see that the fish is not swimming well or feeling uncomfortable, immediately return it back to the original tank.
  • The method is not applicable for the scaleless fish as they can’t bear salt and may die. For that consult veterinary doctor to treat it.

How To Treat Severe White Fluffy Stuff In Tank?

When the infection is severe. Perhaps has been spread around the tank, then it’s essential to treat the whole container (with something like an aquarium water treatment kit (Available On Amazon)

The treatment method includes

  • Measure one teaspoon and dissolve in each gallon of water in the tank. Use a small separate bucket to do so.
  • Slowly add the solution in the tank.
  • Change 25% of water weekly.
  • Do not add extra salt when you start the treatment
  • Continue till you see a complete disappearance of the white moulds in the tank.
  • Do not use the slat at home always prefer to buy the special aquarium salt having a consistency that the fish can resist.

Severe White Fluffy Stuff In Tank

Things To Focus

  • Measure the right quantity of the salt.
  • Make sure the salt is completely dissolved in water.

How To Treat White Fuzzy Stuff On Aquarium Decorations

If you have white fuzzy stuff on decorations in your aquarium it is important to clean them in a certain way.  To clean them 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 (Available On Amazon)
  • Wait for 1 hour
  • Remove the ornament and rinse again with hot water
  • Put back in to aquarium

Treat White Fuzzy Stuff On Aquarium decoration

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

How To Clean White Fungus On Aquarium Plants

White fungus is very dangerous to fish, if your plants have white fungus on them you need to remove the plants from your aquarium as soon as you can. Your fish will eat the plants and white fungus and can then become very ill.

White Fungus On Aquarium Plants

The early signs of fungus on the plants include the leaf edges looking hazed and worn out (Source)

If you have white fuzz or fungus growing on your aquarium plants I highly recommend you to remove the plants and throw them away.

If you want to treat the plants for fungus you will need to do the following.

  • Remove plants from aquarium
  • Place in to a small tank with no fish
  • Apply an aquarium water treatment kit (Available On Amazon)
  • Raise the temperature of the aquarium (This will help to kill the fungus and bacteria)
  • Wait a few days
  • Add some aquarium salt to the tank
  • Wait a few days
  • Make sure the water is clear and not white fuzzy looking
  • Place the plant back to the original tank

How To Clean White Fuzz From Fish Tank

Once you have taken the above steps to remove the white molds / blobs from your tank we will then need to refresh the water in your tank.

Clean White Fuzz From Fish Tank

  • Shift the fish to the quarantine tank with optimum temperature and pH so that it feels no distress in the new environment.
  • Take out all the decorations and fresh plants. Keep them away from the quarantine tank
  • Drain whole water. Try to drain outside the home so that no leftover spore can reattack to fish or tank.
  • Scrap the particles and residues.
  • Use the high-quality detergent to wash the tank thoroughly
  • Drain the soap and rinse two to three times with hot water. Make sure there is no leftover detergent, and the tank is cleaned thoroughly.
  • Place it under sunlight to dry as well as to remove any smell.
  • Meanwhile, wash the tank decorations. First, scrap all residues. Then soak in detergent to thoroughly clean.
  • Rinse with hot water two to three times.
  • Let them dry and place back to the already treated tank.
  • Fill the tank with water having nutrients optimum for the fish. Do not add water having chlorine, ammonia or nitrite in it.
  • Maintain the temperature of the tank.
  • Allow the fish to swim again in their tank.

How To Prevent Mould  / Fungus / Bacteria Infection In Your Tank

Now we have removed all the bad white mould / fungus from our tank we need to take steps to make sure it doesn’t come back again.  Follow these steps

  • Keep water clean and hygienic. Change it every two to three weeks.
  • Do not overfeed your fish. Commonly 15 minutes of feed is enough. Otherwise, the leftover becomes food for fungus and bacteria that give rise to cotton colonies.
  • Keep an eye on fish activity, if you feel that if it’s not swimming well or hiding behind the things, it means something wrong with it. Immediately check, so it gets treatment on time. Moreover, you will prevent the spreading of infection to the whole tank.
  • Apply a water conditioner once every 2 weeks to your tank
  • Make sure the filter system you have in your tank is powerful enough for your tank

These are few caring strategies that you should adopt; otherwise, your fish tank may get infected and may create a frustrating condition for you.

How Do I Get Rid Of White Algae In My Fish Tank?

White algae will appear in your tank because there is some sort of imbalance with your water conditions. Once you work out what the imbalance is you will need to know how to get rid of white algae

The best way to get rid of white algae from your fish tank is to change 50% of the water, then apply a water conditioner to the tank and wait a few more days for the algae to disappear.

If you still have white algae in your fish tank after applying the above you will need to perform the following tasks.

  • Remove larger white algae from tank ornaments / driftwood / tank glass with a brush
  • Remove tank ornaments / driftwood and wash them under warm water from the tap
  • Permanently remove any plants that has white algae on them from the tank
  • Change 50% of the aquariums water
  • Apply a water conditioner to the tank

What Does White Algae Look Like?

White algae will usually look like a slick film or slimy white cotton like substance which usually starts to form around objects in your tank such as plants, driftwood and the tanks glass.

Below is a picture showing what this algae looks like in a fish tank

What Does White Algae Look Like

What Causes White Algae To Appear In My Tank?

White algae will appear in your tank because there is some sort of issue with the water condition. The best thing to do is use a water tester kit (You can get some good cheap tester kits from amazon) to identify what is causing the issue.

The most common issues include

  • Tank in direct sun light
  • Water to hot

Frequently Asked Questions

How to remove white algae from aquarium?

The best way to remove white algae from your aquarium it to change the water often and make sure to clean out your tanks filter. You can remove larger algae with a scrubber.

White Cotton Like Stuff in Fish Tank Treatment?

The best treatment for white cotton like stuff in your fish tank is a fungus aquarium treatment. Also changing the water will help.

Why is There White Stringy Stuff in my Fish Tank?

The white stringy stuff in your fish tank is fungus that is growing from overfeeding your fish, Which in turn causes poor water conditions which is perfect for fungus growth.

What is the White Fuzzy Stuff in my Fish Tank?

The white fuzzy stuff in your fish tank is known as cotton wool disease which is fungus growing in the tanks water. The fungus will look white and fluffy or fuzzy

Why is There White Algae in My Fish Tank?

The most likely reason for white algae in your fish tank is poor water conditions that are present that usually appear when you are over feeding your fish


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

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