Identifying the White Spots That Appear on Fish (illustrated)

One day you pass by your aquarium and notice that your goldfish or Betta is covered in something unusual.

Be they large or small, any form of white spots appearing on the body, fins or tail of a fish are a cause for concern.

Your pet has likely become the host of a common pathogenic parasite known as ich or ick, but that’s not always the case.

This illustrated guide will help you identify the possible reasons behind these skin diseases and offer pointers on what to do next.

Skin spot diseases are prevalent in tropical fish aquariums where these conditions progress faster because of the favorable water temperature.

The best and fastest treatment is a function of a timely, yet proper, diagnosis.

Diagnosing white growth depends on its appearance and body locations.

Does the spot look like it’s made from fuzz or a slimy film? Would you describe it as large patches, random clusters, or tiny dots?

All of these signal different conditions which are a potential threat to a fish’s life.

Why are there white dots appearing on your aquarium fish?

If the dots appear to be tiny and round it means that the fish has contracted an external protozoan parasite that feeds off of its flesh.

The mortality rate of this condition is extremely high and measures should be taken as soon as possible.

Here’s the reason behind white spots appearing on aquarium fish:

The most common cause of tiny white spots forming on the fins, gills or the body of aquarium fish is a pathogenic parasite known as ich or ick. The parasite forms microbial cysts which are sheltered under the outer skin layers of the host fish, resulting in convex white lesions with a diameter of up to 1 mm or 0.04 inches. Each of these bumps resembles a small white dot, which looks like a grain of salt or sugar, hence this parasitic outbreak is often referred to as white spot disease.

Unless the disease spreads outside of the gills, it will not visually manifest itself as white dots.

The next picture will help you identify ich by showing how its white round dots look like on these two goldfish:

By Fallowart

Here’s how the advanced stage of freshwater ich appears on this gourami fish:

By lordoftime

Have a look at the initial stage of marine ich manifesting itself as small dots appearing on random body locations in a Purple Tang fish:

By ScubaZ

And here’s a photo of a more severe case of marine ich on another saltwater fish:

By Mrcote1

The white spot disease is known to affect the large majority of both freshwater and saltwater fish, and no species is known to have developed a natural defense mechanism against it.

In freshwater aquariums, the disease is caused by a protozoan parasite from the group of ciliates called Ichthyophthirius multifiliis.
In saltwater aquariums, the parasites responsible for what’s known as marine ich are named Cryptocaryon irritans and are also ciliated protozoans.

Both parasites share the same life cycle, however, the time to complete it varies based on water temperature, affected fish species, and water salinity.

How should you cure it?

Most commercially available chemicals that treat external protozoans such as the ones responsible for ich will show success in both freshwater and saltwater fish tanks. For the best results, these should be combined with increasing the water temperature of the aquarium.

The commercial products will often contain malachite green, a 37% formaldehyde water solution known as formalin, copper or any combination of three.

In freshwater aquariums, I personally have had success with Hikari Ich-X for more advanced stages and Weco Nox-Ich if I happen to catch the condition in its early phase.

Click here to learn more about treating Ich in freshwater fish.

The preferred methods for treating saltwater Ich are copper-based medication and inducing hyposalinity.

Learn more about treatment methods for Ich in saltwater aquarium fish.

Ich is highly contagious among fish in confined spaces and it should be treated as soon as it is noticed.

If left untreated for long enough this disease can reach up a 100% mortality rate.

What if the condition is NOT caused by Ich?

If the white formations on your fish appear like larger patches, that have a fuzzy texture, or the dots are too dense to count then you may be looking at fungus outbreak or a bacterial infection. The latter include deadly infections such as Columnaris.

In some cases even viruses such as Lymphocystis will cause such symptoms.

White spots that are NOT caused by Ich may appear on fish with the following diseases:

1. Severe Velvet Disease

The Velvet disease affects both freshwater and saltwater fish and is caused by different single-celled dinoflagellate parasites, which are essentially classified as algae.

An infected fish will appear as if it’s covered in white or gold dust particles.

Not to be mistaken for Ich, the white dots of Velvet disease will almost completely cover a fish’s body. These spots will appear finer and more dust-like, unlike the ones caused by the Ich parasite.

Take a look at this photograph of a Purple tang with a Velvet disease which appears to be covered in fine white powder-like particles:

By Humblefish

And now have a look at a Betta fish that’s infected by the freshwater Velvet parasite:

By Araxie

See here how the white dots appear as dust:

By Staisman

Aside from the physical manifestation of Velvet, the symptoms in fish are very similar to those of Ich.

An infected fish will gasp for air, and it will try to scratch its body in aquarium decorations or the substrate while flashing around with erratic movements.

With the progression of the disease, lethargy will overtake the fish and it will completely lose its appetite.

Because of the extremely fast progression and high mortality rate of this disease, treatment should be launched as soon as there’s a diagnosis.

Treating Velvet is very similar to treating Ich and it usually includes products such as copper sulfate for marine Velvet, methylene blue and formalin for both freshwater and saltwater aquariums, the addition of salt and rising the water’s temperature.

The aquarium lights should be tuned down during treatment as the Velvet parasites have photosynthetic abilities.

2. Lymphocystis virus

A virus from the genus Lymphocystivirus is responsible for the viral disease Lymphocystis, which affects marine and freshwater fish alike.

It manifests itself as white growth on the skin of aquarium fish, which resembles white irregularly-shaped dots, that later grow into large asymmetrical spots with a cauliflower-like appearance.

In its early phase, the white formations of the Lymphocystis virus tend to cover the fins of the fish and until developed will appear small and round. For this reason, in its initial stages, the nodules of Lymphocystis are often mistaken for ich but the two do not have anything in common.

Have a look at the already-developed white nodules on the fins and tail of a German Blue Ram infected with Lymphocystis, and notice how they do not resemble ich:

By Dunk2

The only other symptom of Lymphocystis is the fish experiencing physical discomfort from the nodules covering its gills or mouth. This could potentially lead to difficulties in absorbing oxygen from the aquarium’s water.

Unfortunately, there are no known cures for this virus.

However, mortality rates are very low and death may only occur from secondary fungal infections.

Upon spotting the white growth, simply try to improve the water quality of the fish tank, and feed with high-quality foods, supplemented with vitamins such as VitaChem.

In a healthy aquarium environment the Lymphocystis virus will eventually subside on its own.

3. Freshwater Neo Ich

The neo ich is a new species of a recently discovered parasite causing white spot disease.

The condition is not caused by Ichthyophthirius multifiliis, which is responsible for normal ich, but rather Ichthyophthirius schlotfeldti.

This freshwater pathogenic parasite is characterized by very dense clusters of small white specks that appear identical in size to those caused by the normal ich.

The initial stage of the infection could manifest itself as a grey coating instead of dots.

Sometimes, because of the sheer density of the spots, Neo ich is also mistaken for Velvet disease.

Velvet’s specks are way smaller and resemble powder, instead of grains of salt.

The difference between the two Ich parasites is that neo ich can reproduce inside the host and does not need to leave the skin of the fish during its life cycle.

Neo ich also has an incubation period of 1.5 to 2 months and has a slower development even at elevated water temperatures.

Have a look at this discus fish infected with Neo ich, almost completely covered in white dots, but the cluster is not as thin as the one normal ich would cause:

By Husky_Jim

The behavioral symptoms of Neo Ich sometimes referred to as Neoichthyophthirius, are identical to those of normal ich.

They include scratching on objects, random dashing around the aquarium, loss of appetite, and gasping for air because of blocked gills.

The treatment of neo ich is very difficult because the parasite remains shielded behind the skin of its fish host.

There are some suggested treatment methods such as repeated doses of malachite green supplemented with acriflavine.

Since this parasite doesn’t have a vulnerable stage of life very high mortality rates are expected.

4. Brooklynella disease

The Brooklynella disease affects marine fish but tends to mainly infect clownfish.

The disease is caused by an external protozoan parasite called Brooklynella hostilis.

Brooklynella is characterized by white mucus building up on the skin of fish. At first, the white slimy-looking film will appear at certain areas of the fish’s body, but with the progression of the disease it can cover the whole host.

Here’s an initial stage of Brooklynella on a clownfish, forming a large spot of white mucus behind its fin:

By aboy461

Take a look at a close-up of the film that’s covering another clownfish infected by the Brook parasite:

Look at a Naso Tang that has contracted the Brooklynella parasite and how the affected areas secrete white slime, appearing as if the skin is peeling off:

By HumbleFish

The Brooklynella parasite primarily targets the gills of fish and eventually starts spreading throughout the whole body.

Behavioral signs showing a fish is infected begin with fastened gill movements, staying close to the surface of the aquarium, and trying to scratch on objects. Loss of appetite, lethargy and fading coloration are also symptoms of an infection.

The most effective known treatment for Brooklynella is a formalin bath with a duration of 30 minutes to 1 hour, depending on the severity of the disease.

After that keep treating with lower formalin doses supplemented with metronidazole or Seachem MetroPlex in a quarantine tank for at least 2 weeks.

5. Stress spots on Tang Fish

Saltwater Tang fish are very fragile and sensitive to the water parameters of their aquarium. Sometimes environmental stress will cause a Tang fish to display discoloration which resembles white polka dots. None of these spots will be raised and they will appear significantly larger than the small granular cysts typical for ich.

Stress spots tend to affect the Naso Tang the most, however, they can be seen on a wide range of Tang fish such as the Powder Blue Tang, Kole Tang, Hippo Tang, and others.

Have a look at how the white circular spots look on a stressed Naso Tang:

By Submerged

And here you can see a powder brown Tang that has acquired his white dots after stress from transportation:

By marcusbacus

And another Naso Tang having what appears to be large white polka dots from a stressful event:

By Mr.tang999

Such stress spots in Tangs will come and go and are not a direct threat to the fish’s health.

However, the white blots are a good indication that the Tang’s environment has been stressful, which subsequently leads to a weakened immune system and other infections and disease.

Stress spots commonly appear after transportation from the store, in aquariums with aggressive tank mates, after large water changes, and temperature fluctuations.

6. Columnaris

Columnaris affects freshwater fish and is caused by the Flavobacterium columnare bacteria, however, it’s often mistaken for a fungal infection.

The visual symptoms of Columnaris are white standalone patches forming on the fish’s body and back. These spots may look like thin film but are actually lesions. Each spot will lack a slime coat, meaning that they won’t reflect light the same as the rest of the fish’s body.

Take a look at how the white patches of Columnaris look on this infected Betta fish:

By CurryGremlin

Here’s a photograph of a pleco that has developed unnatural white spots that resemble a thin film covering its back, which are likely caused by the Columnaris bacteria:

By Atfaught50

Have a look at another example of white patches forming right next to the gills of this fish:

By mgaguilar

Some of these white lesions can form around the fish’s mouth and appear raised with a cotton-like texture.

This is often when the Columnaris disease is confused with fish fungi.

And here one black moor and one gourami that both have the white fungus-like growth around their mouths, which is actually Columnaris:

By thesametarts and OliverandMalmo

Other symptoms of Columnaris in aquarium fish are darkened rotting gills, white mucus accumulating on the fins and gills, frayed fins, rapid breathing, and gill movement.

The treatment of this disease is as difficult as it is to diagnose it.

Treat immediately with bacteriocidal antibiotics, such as oxytetracycline also known as Terramycin.

Another good option would be a combination of kanamycin which you can find in Seachem’s Kanaplex and Nitrofurazon, which can be found in API’s Furan-2.

Be sure to relocate the affected fish in a quarantine tank, because the antibiotics will also harm the aquarium’s beneficial nitrifying bacteria.

7. Fungal infection

Fungal infections in aquarium fish are often the result of a previous illness such as parasites or bacterial outbreaks.

Visually, fungus will manifest itself as white fuzzy growth, forming a single or multiple individual patches on the fish’s body, fins or gills. The fungal patches always resemble cotton fuzz or white mold in color and texture and will never look like dots or film.

You can see how the white fuzzy growth appears behind this betta’s gills:

By yambercork

And here’s a severe fungal infection looks on another Betta:

By Kadi

Fungal infections are found more often in freshwater aquarium fish than in saltwater ones.

Though rarely, fungus can infect a marine fish forming the typical white and woolly-looking spots.

By Murica

Fungus can eventually kill a fish, but it’s easily treatable with commercially available products such as API PIMAFIX.

To treat light fungal infections in hardy freshwater fish you can slowly raise the water temperature and dose aquarium salt.

However, fungus always appears after something else was wrong and it is recommended to first eliminate the underlying reason.

Test the water parameters for fluctuations, see if there are wounds from fighting or sharp aquarium decoration, signs of bacterial infections or external skin parasites.

8. Parasitic Flatworms known as Flukes

What’s known in the hobby as flukes is actually parasitic flatworms with many different species often infecting marine fish, but freshwater aquariums can also be affected.

Though they won’t be visually present on the fish’s body at first, flukes will become apparent during the treatment of a host that shows ill symptoms.

Check this photograph of a clownfish that has its flukes already apparent:

Also, see a close-up of the white raised blister-like areas on a fish’s fin:

By HumbleFish

Here’s how flukes that are leaving their host after a freshwater dip look like to compare with marine ich:

By hakofucu

The signs of infestation with flukes are fish flashing around the aquarium, scratching on objects, pale color, stringy feces, swimming near the water surface, lethargic behavior and troubles breathing with a rapid gill movement.

If an aquarium owner suspects that their saltwater fish is infected, he or she should perform what’s known as a freshwater dip.

That’s dipping the supposedly ill fish in highly oxygenated fresh water for 5 minutes.

Freshwater dips force flatworms to leave the skin of a marine fish, making it look as if its body is covered in raised spots that are white to transparent and resemble sesame seed.

A common treatment of skin flukes for both saltwater and freshwater fish is the use of Praziquantel, chosen for its efficiency against these parasites.

The recommended go-to product that contains that is usually PraziPro.

9. Missing scales

If an aquarium fish has white, randomly-distributed patches that look slightly concave then it may be experiencing scale loss.

Missing scales or flesh rot leave behind an exposed scaleless spot on the fish’s body that often appears white to light grey, but may later become red.

For identification purposes, here’s a photo of a female swordtail missing a couple of scales:

By HeyIDoWrk

Also have a look at this goldfish that has a white patch of missing scales:

By countrychick

Missing scales in aquarium fish can be caused by a plethora of factors including but not limited to:

  • Aggression between fish tank mates.
  • Injury from sharp decorations.
  • Scratching on surfaces, because of a skin parasite.
  • Flesh rot from bacterial and fungal infections.
  • Long-term exposure of the fish to high nitrates, which is known to cause Head and Lateral Line Erosion (HLLE).
  • Long-term use of activated carbon in the aquarium which has been suggested to increase the possibility of Hole in the Head disease (HITH).
  • A diet that’s low on vitamins

To identify what’s behind the mysterious white patches of missing scales you will need to monitor the fish for other behavioral symptoms.

A Siamese Algae Eater that misses some scales possibly caused by Hole in the Head (HITH) disease:

By Unboltthebulls

Treatment and Prevention

There are various possible causes of a fish that has developed white specks or patches on its body, fins or gills.

Additional behavioral symptoms will help in identifying the cause in order to begin an adequate treatment.

Here are guidelines to follow when you want to treat an aquarium fish for white spots:

  • Most external skin parasites in aquarium fish can be cured with chemicals such as copper sulfate, malachite green, methylene blue and the slightly stronger formalin.
  • Bacterial and fungal infections should be treated with antibiotics and anti-fungus medicine respectively.
  • Aquarium salt is usually beneficial for skin parasites in freshwater aquarium fish, but will not be enough as a sole method of treatment. You can certainly use kosher or rock salt, but nothing that has iodine in it (like most table salt), as fish get it from their food and you don’t want it building up in their system.
  • Raising the water’s temperature is always beneficial when treating external protozoan parasites, because it makes them vulnerable faster by speeding up their life-cycle.
  • Freshwater dips are very effective against some common external parasites in saltwater fish, but will not be enough to treat the condition on their own.
  • Most antibiotics can also obliterate beneficial nitrifying bacteria in the aquarium. Therefore an antibacterial treatment should always be carried out in a separate hospital tank.
  • UV sterilizers and activated carbon media can both hinder the effectiveness of a medicine by capturing or altering its molecules. Remove them before the treatment.
  • Always follow the instructions on your medicine of choice.

Treating fish with any form of white spots can be quite straightforward as long as the diagnosis is right and timely.

It’s way more important, however, to be able to prevent future outbreaks.

Maintaining excellent aquarium water quality and a proper diet for your fish can be the difference between an aquarium crash and a long-term hobby.

Setting up a quarantine tank where you can monitor the behavior of new fish additions is one of the best ways to prevent spreading illness in your display fish tank.

It’s literally the stress

Usually, well-nurtured fish have very strong immune systems and are able to keep almost all parasites and bacteria at bay.

Most of these vermin are always present in an aquarium and only manifest themselves when they find a weakened host.

The reason a fish would develop a weakened immune system is environmental stress.

Here’s what makes a fish prone to disease:

  • Stressful shipping and transportation.
  • Stress from aggressive tank mates or overcrowding an aquarium.
  • Poor water quality, including constant nitrate levels of above 10 ppm.
  • Unstable water parameters, including pH.
  • Wrong or imbalanced diet that does not include vitamins.
  • Water temperature fluctuations which usually happen during Fall and Spring.

Be prepared for casualties

A big part of successfully curing most of the aforementioned diseases is spotting them on time.

If the fish has already developed a white external formation of some sort it means that the illness has been around for a while.

The sooner you diagnose it and start the treatment the better chances of survival for the fish.

However, quite a few of these conditions have high mortality rates and it’s not unseen to lose a fish even after you’ve started treating it by the book.

Be mentally prepared for a grim ending.


There’s no time to lose if you want to save your aquarium pet so if you’ve identified its disease based on the explanations above, I suggest treating it immediately.

Any unusual new spot on your fish, be it white or another color is worth investigating, and most of them can definitely be cured.

Comment below if you need more answers, but make sure to describe the affected body area in detail and provide information on the water parameters and recent changes made to the aquarium.

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