As a dedicated aquarist, you must provide your tank with great care and attention. This includes ensuring the environment in the tank remains conducive enough for the plants and fish to thrive.

But with all the care you provide, what happens when you notice some white stuff floating in the fish tank? What could be the possible reasons and solutions to this?

While some of the causes are pretty natural, others may indicate a lack of attention on your part.

This article takes an in-depth approach to this problem and some workable solutions.

fish-tankReasons Why White Stuff Is Floating In Your Fish Tank

Not all white particles floating on the tank are the same. Some may be long and whitish, some string-like, and others appear like cotton. Some of their sources could be anything from the list mentioned below

1. Decomposition Of Plants And Fish

fish-debrisWhen fish and plants die in the tank and are not removed immediately, the decaying debris can begin to disintegrate and float all around the tank.

2. Excess Fish Food Decomposing

Overfeeding your fish can lead to a buildup of uneaten fish food floating in the tank as it starts to decompose. Sometimes, it may dissolve and then release protein and fats.

3. Water

If you use tap water or any water with some iron or dissolved mineral components, they can become oxidized and form a white layer in the tank. It happens due to the oxygen present in the tank.

4. Faulty Filter System

If the tank filter isn’t working correctly and cannot eliminate all the waste produced in the tank, chances are high it will remain there floating on the top.

5. Worms

worms-in-tankThe white stuff floating in your tank could be worms, especially if those whitish particles move.

This is quite normal when you put new plants and fish in the tank. They are known as planaria and detritus worms.

While detritus worms (which appear like a brownish-white string that’s pointy) are not harmful to your fish, it is essential to get rid of them because they feed on plants and make the tank look dirty and displeasing.

6. Overcrowded Fish Tank

overcrowded-tankOccasionally, this whitish particle may be fish waste. This waste looks oily and results from the fish’s digestive system breaking down food into protein and oil.

The more crowded a fish tank, the more waste is produced. This fish waste accumulates over time, becoming unpleasing to look at.

Even when you clean your tank, you may find it dirty again within a short period.

7. You Just Cleaned Your Tank

If you’re new to owning a fish tank, this might come as a surprise but is quite normal. After you finish cleaning your tank, there can be something resembling dust particles in there.

These particles are the debris that got in the substrate while adding clean water into the tank.

It should clear on its own after a couple of hours. However, something is not normal inside the tank if it doesn’t.

8. External Particles

If your fish tank is placed where a lot of dirt and particles can come in, chances are the stuff floating in the tank is from your surroundings.

Cooking oil, dust, or bugs can easily get into the tank and contaminate the water.


1. Make Use Of Chemical Filtration

If the water composition is causing the white stuff in the tank, then chemical filtration is the most helpful solution. It involves the use of activated carbons, which pull all the dissolved organics from the water by adsorbing them.

However, it is important to note that some activated carbons alter pH levels. Steer clear from those and go for acid-washed carbons.

These activated carbons can get through fatty substances, get rid of dissolved proteins, chloramine, chlorine, and reduce terrible smells coming from the tank.

Maintaining the fish tank is less stressful and less demanding with this kind of filtration.

2. Use Flocculants

flocculantsFlocculants are a great option to get rid of those white particles that look like dirt. They are not made with chemicals making them entirely safe for your plants and fish.

Flocculants cause particles to stick to each other, making them clear and big enough to be removed.

Go for a variant that is odorless. It also shouldn’t have any harmful chemicals, not even alum.

After use, make sure you clean your filter because the particles will clump there.

3. Avoid Overfeeding Your Fish

It is advised to feed your fish once or twice a day. Overfeeding can lead to the rapid accumulation of digestive by-products in the tank.

It is also typical for hobbyists to fast their fish once or twice a day each week to allow their digestive system to clear.

This, however, doesn’t mean you should starve them. In fact, how you feed them should depend on the kind and size.

4. Use An Air Pump

To make sure bubbles are forming in the tank, use an air pump with an airstone. This will prevent oil and white particles from floating on the surface.

Also known as a bubbler, this equipment supplements oxygen levels and fastens water circulation in fish tanks.

5. Filter Floss

Good filter floss is an excellent investment for your fish tank. It is a fabric that prevents large debris from getting into your filter pump.

This filter floss can grasp the finest particles and prevent them from floating around in the tank.

Because it is placed before the filter, filtration has to begin from the filter floss before getting to the pump.

As a result, it gets clogged quickly. It is advised to change them every five days. However, the process is fairly straightforward.

6. Surface Skimmers

This device can get rid of mold and oil films on the water surface. This should not be confused with protein skimmers which remove organic compounds and fine proteins.

Surface skimmers make the water surface clean and promote oxygen exchange.

Other Whitish Stuff That May Float In Tanks

white-stuff-floatingIf the white stuff you see is cotton-like, the reasons for this can include:

  • There’s a fish in the tank with a bacterial infection or rotting fin.
  • The temperature of the water is left uncontrolled.
  • The tank is filthy. Water not being changed often and overexposure to a dirty environment could be other reasons why white cotton-like particles appear in your tank.
  • Leftover fish food has led to a buildup of bacteria, algae, and fungi.


  • Pay close attention to the fish in the tank and make sure they are swimming correctly. If you notice anything strange, consult an aquatic vet.
  • Get another bowl or tank of water to separate the healthy fish from the diseased ones. Treat them properly before putting them back in the tank.
  • You can install a heater in cold weather to control the water temperature. Also, have a thermometer to know the right temperature for your tank.
  • Make sure you clean the tank often and adequately. Keep your tank away from dusty surroundings.
  • Do not overfeed your fish. When you notice food leftovers, use a fish net to filter them out instead of leaving them to decompose.


The presence of white particles in a fish tank is quite a common occurrence. However, irrespective of the source, these particles may pose a threat to the overall well-being of your tank.

When you notice them, try to identify their source and use the solutions mentioned above.

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