Ich or White Spot Disease

Many aquarium fishes are susceptible to fish disease. The most common fish diseases are caused by various parasites such as Protozoans, Cestodes, Nematodes, Trematodes, Crustaceans, and Acanthocephalans. Generally, fishes serve as a host for the different type of parasites causing disease.

Types of Fish Disease

There are different types of fish disease:

Parasitic Disease: Parasitic diseases are caused by the infection of Protozoans, Metazoans, Cestodes, Nematodes, Crustaceans parasites etc. The most common parasitic diseases are ich or white spot disease, Chilodonelliasis Costiasis, Myxosporidiosis, Coccidiosis, Cryptocaryosis, Argulosis, Lernaeasis, Dactylogyrosis etc. 

Bacterial Disease: Bacterial diseases are common in many aquarium fishes. The most common bacterial diseases are the ulcer, hemorrhage, and septicemia. Many bacterial pathogens causing infection are associated with virus and fungus.

Fungal Disease: The most common fungal diseases are Saprolagiasis,  Branchiomycosis, and Aphonomycosis. Causative agents of fungal diseases are Saprolegina sp, Achyla sp., Branchiomycess sp., Aspergillus sp., Exophiala sp. Etc.

Environmental Disease: Many fishes are affected by different types of environmental factors. The presence of harmful impurities in water is mainly caused by the influence of environmental factors resulting fish diseases. A number of abiotic factors are also responsible for the creation of abnormal behavior to fish as well as serious diseases.

General Preventive Measures of Fish Diseases  

To reduce the possibility of diseases to your fish, you should take some preventive and precaution measures that help keep your fish healthy. 

  • You should buy good quality fish from well-known fish traders;
  • You must quarantine new fish before adding to the aquarium;
  • Overfeeding should be avoided;
  • Identify sick fish and transfer it to the quarantine tank for treatment;
  • Before moving sick fish, disinfect the fish nets;
  • Water should not be transferred from the quarantine tank to the main aquarium;
  • To keep your fish healthy and disease free, you should maintain balanced diet, good water quality parameters and correct stocking densities.
  • For proper fish health, you should always maintain food with essential nutrients. In this case, large ranges of food with different forms guarantee the better nutrition of your fish.

Role of Temperature to Control Disease

Water temperature is a very important physical factor which plays a great role to maintain fish health. Sudden water changes affect the immune system of fish causing parasitic infections or environmental diseases.  Generally, tropical fish requires the suitable temperature which ranges from 75-80° F (24-27° C).

If the temperature fluctuates +/- 30 from the suitable ranges which makes your fish susceptible to diseases such as ich. For constant water temperature in your aquarium, use good quality heater and thermometer which are available in the pet fish market with sensible cost. In this case, regular water temperature should be checked to ensure large water temperature fluctuation does not occur.

Role of Water Quality Parameters to Control Disease

To maintain good health of fish, water quality parameters play a big role.  To make your tank water quality good for fish, 20-30% water changes should be done daily which reduces nitrate buildup, eliminate debris and waste materials and ensure sufficient oxygen for fish. In this case, use water testing kits to ensure good water quality in your tank.

Ich or White Spot Disease

Diseases caused by protozoan parasites are mainly Apizoma, Trichodina, Chilodonella, Ichthyobodo, Ichthyopthirius multifilis, Epistylis, Costia, Myxobllus, Myxosporidians. Rapid multiplication of the protozoan parasites on the host leads to a severe infection that soon weakens fish and fry results in high mortality. Protozoan parasites are most common in all ages of fish. Cyprinids fingerlings are common victims of protozoan parasites. 

Among protozoan diseases, Ich or white spot disease is caused by ciliated protozoan parasite ‘Ichthyophthirius multifiliis’. It is a very common disease of aquarium fish which is also known as Ichthyophthiriasis. Ich outbreaks occur when you introduce a new fish to an established aquarium without doing quarantine.

Ich or Ichthyophthirius multifiliis is an ectoparasite which lives on the outside of the host body and forms small white salt grain like nodules on the body, fins, and gills of the fish. This white dots or white grains of salt gave the nickname, ‘white spot disease’.

This type of parasite affects the fish if your tank contains bad water quality. When only one new fish carries this parasite, it spreads among all of the tank-mates causing fatal secondary infections. This parasite has three stages life cycle which is significant to recognize for proper identification and treatment.

Life Cycle of Ich (Ichthyophthirius multifiliis)

Tomont phase: Ich becomes adult in the host fish. This adult form is also called tomont which leaves the fish body and attaches to the aquarium bottom or other surfaces to form a thin-walled cyst. In the cyst, they split several times and produce about 2000 tomites.

Theront phase: After breaking cyst-wall, the tomites release from the cyst into the water. At this time, they become elongated in shape and forms theronts. These theronts have cilia which help to swim close to the fish host and enter the epithelium of the fish body by using a penetrating gland. Hence, this stage is also known as thermonts or swarmers.

Trophont stage: After penetrating the host body, they fed on the host fish and become mature to reproduce again.

Ich or White Spot Disease

Life cycle of Ich

Generally, the theront and tomont stages show sensitivity to treatments in the water. Its life cycle mainly depends on water temperature and they infect the fish if the tank contains water temperature between 20 and 240 C (68 and 770 F). Naturally, Ich does not replicate at water temperatures above 300 C (850 F). Thus, they do not create any problems to the fish during the warm summer months.

Identification of Ich

Diseased fish shows one or numerous white salt grain like spots on the outside of the body, fins, and gills. It can easily spread among all of the tank-mates.  You can also identify the white spot disease by observing the following signs:

  • They produce excessive slime;
  • Clamped fins;
  • Fish rubs against decorative objects like rocks and gravel
  • They try to rest on the bottom;
  • Loss of appetite;
  • They show abnormal swimming behavior close to the surface;
  • Breathing occurs rapidly;
  • Hiding abnormally;
  • They move individually;
  • Refusing all food;
  • Fish become tired due to abnormal movement;
  • In advanced stages, bloody streaks or redness are seen;

Treatment Options

When one or more fish are susceptible to ich, you should start treatment your fish very quickly. You should do 25-30 % water changes daily to fight against ich.

Ich is a highly infectious disease. Generally, it is occurred due to stress and other factors that reduce the immunity of your fish and speed up an outbreak of Ich. You can lessen the disease or remove the ich from your fish by increasing the tank temperature up to few degrees.

This treatment is only suggested for fish that can deal with higher water temperatures; it is not appropriate for cold-water fish such as goldfish. Treating individual fish with salt baths or adding aquarium salt to your tank can also help to kill or remove the external parasite or ich. You should just follow the dosing instructions carefully and remove any activated carbon from your filter before dosing your tank.

Besides these, different types of medications are very effective against Ich including methylene blue, formalin, copper sulfate, malachite green, and potassium permanganate. You should also keep the water quality high in your tank and feed the balanced diet to make your fish disease free and keep them in good health. You should also quarantine new fish for at least two weeks before adding them to your tank.

Treatment of Ich Using High Temperatures

If your fish is affected with ich, you should raise the water temperature of the fish tank. Because high temperature accelerates and interrupts the life phase of parasite and finally kills the ich. Recommended temperature for killing ich is 85 degrees F (29.5 degrees C) or higher.

When treating with high temperature, you should carefully maintain the temperature. All fish cannot survive above temperatures and you should give enough time to adjust the temperature. During the treatment with high temperature, it downgrades the oxygen levels of your tank water and may kill the fish if you do not take appropriate care. In this case, the raising of temperature should not more than 2 degrees above normal temperature.

If you detect any sign of Ich, you should continue treatment for at least 3 days to kill the parasites. You should install the air pump to create aeration in the aquarium because warm water does not contain sufficient oxygen. In this case, fish does not take breathing easily due to the damaged gills by the parasites. To get sufficient oxygen in the aquarium, you can also install the internal filter to create agitation in the aquarium water.

Treatment of Ich Using Salt

Salt treatment is a very effective method to treat ich or white spot disease.  Generally, salt interrupts the fluid secretion of ich and helps to increase the natural mucous secretion and make slime coat against ich.  To treat ich with salt, you always use pure NaCl with a dose of one tablespoon per 5 gallons water or 3-5 grams salt per liter of water for two weeks. In this case, you can use aquarium salt which is available in the pet fish market with reasonable price. 

Salt should be dissolved in some warm water and add to the tank water slowly which helps to adjust the fish with salt water. After making a salt solution, use a half dose first time and then use another half dose after about 12 hours. This dose is suitable for salt sensitive fish such as loaches, tetras, discus etc. 

During salt treatment, some fish become lethargic and breathe rapidly. In this case, you should change some water to eliminate some salt from the water. Goldfish and some livebearers such as guppies, platies, mollies, and swordtails respond very well with salt treatment but naked bodied (scale-less) fish does not react well with salt. After each water change, you need to dose for salt again.

Precaution Measures to Use Salt

  • To treat ich with salt, you must use aquarium salt which is especially design for fish. You don’t use table salt because it contains iodine.
  • During treatment with salt and temperature, never use any medication because it lessens the oxygen in the tank water.
  • 25% water changes should be done every few days and add the appropriate amount of salt again. After finishing treatment, change the partial water from the tank and adding of salt does not need again.

Treatment of Ich Using Medications

When salt or high temperature does not work well to stop the ich outbreak, it is recommended to use medication. Before doing treatment with medication, carefully read the product’s label thoroughly to know special instructions, dosage information etc. Besides these, you should also gather warnings related information about own health, aquarium plants, naked bodied fish (scale-less), many sensitive fish and invertebrates.

Before medication, you should do a water change; remove the gravel from aquarium and carbon from the filter media. Carbon reduces the active chemicals from the medication in your tank water. Generally, most of the medications are not more effective due to the presence of unwarranted dissolved organics such as nitrates in the aquarium. In this case, it is instructed that you do not change water from the tank during treatment.

There are different types of medication from different brands for treatment against ich available in the pet fish market with reasonable cost. You can easily eradicate the parasites from the fish body using medication. Generally, ich medication is not safe for some aquarium organisms like snails and shrimp or other invertebrates. If you keep any inverts in the aquarium, you must replace them from the tank during treating with medication. At this time, you should also keep up the high temperature.

Copper-based Medication

It is very commonly used product for treatment against ich. The active ingredient of this medication is copper sulfate or soluble copper salt. Many aquarists highly recommend you to use it for removing ich from the fish body.

It does have some negative impacts during treating with ich. It downgrades the oxygen concentration and it is toxic to inverts such as snail and shrimps. It is also unsafe for aquarium plants and scale-less fish if you do not maintain correct doses. 

This medication is suitable for African rift lake cichlids than other soft-water fish. Generally, the dose of copper depends on the amount of hardness in the water. The following table shows the doses of copper sulfate to treat ich:

Hardness RangeDose
40-50 mg/l   less than 0.25 mg/l
50-90 mg/l   0.50 mg/l
100-200 mg/l   1.0 mg/l

Potassium Permanganate (KMno4)

You can use this medication as a substitute for copper during treating with ich. Generally, it is chiefly used as an oxidizing agent to control of ectoparasites, bacteria, and fungus from the fish body. It is available in the market as Fluke control with sensible cost.

You can also use it to remove the snails and their eggs by adding new plants into the aquarium. It is suitable for treating ich from African Rift Lake Cichlids. But it is not safe for live plants, eggs, baby fish, and catfish fish with high doses and if you do not use correct dose, causing gill damage in adult fish.

It will also spoil the biological filter, lessen oxygen level and kill algae. In this case, strong aeration is needed to make aquarium environment natural. Sometimes it can cause skin and eye burning. As a safety measure, you must use mask and gloves during the application of potassium permanganate. 

Generally, 2 mg/l of KMnO4 is effective against ich or other external parasites. If the tank water contains heavy algal blooms, use a greater dose of KMnO4.


Many freshwater fish cultivators and aquarists use formalin for treating ich. It is harmful to eggs, baby fish, live plants, and scale-less fish with incorrect doses. Sometimes it may spoil the biological filter, lessens the supply of oxygen in your aquarium and damage inverts and the weak fish. 

It is generally used as bath treatment to remove external parasites such as protozoan parasites like ich and monogenetic trematodes from the fish body. If you use formalin with proper doses, it can kill the parasites on skin, fins, and gills. But it is not effective against internal parasites. Generally, formalin is used for bath treatment up to an hour to treat ich. In this case, use 4.4-8.8 ml formalin per 10 gallons water.

Malachite Green

It is one of the most effective chemicals against ich or white spot disease of fish. In the pet market, it is available as benzaldehyde green, aniline green or china green with reasonable prices. It is hazardous to handle and before using it, you should carefully read the instructions and use correct dose. Overdose may cause hazardous for aquarium fish. In this case, use 1 teaspoon or 5 ml per 10 gallons of water to get rid of ich or white spots disease quickly.

It is not safe for eggs, baby fish, and some species of catfish, loaches, tetras, and small-sized saltwater fishes. It can also spoil the biological filter media and aquarium decorations. It is recommended to keep aquarium light off during the period of treatment due to its light-sensitive nature. 


It is also highly effective against ich or white spot disease. It is available in the market as a different name such as Acriflavin Plus, Ick Clear, etc with reasonable cost. It is not safe for live plants, invertebrates, scale-less fish and other sensitive fish. It may also damage the biological filter and tank decorations. You should remove the live plants and other sensitive organisms from the aquarium during treating ich with this medication.

The general dose of Acriflavine should be 1 teaspoon per 10 gallons of water. To get a better result, you should treat your fish every other day for up to 10 days.

Methylene Blue

You can use it for the treatment of ich and other protozoan parasites such as Chilodonella and Costia. To treat ich, use 1 teaspoon of methylene blue for 10 gallons of water or 10 drops for 1 gallon of water. It is safe for eggs, baby fish and sensitive fish. It may damage biological filter, live plants, and tank decorations. It is recommended to change the aquarium water after completing the treatment.

Some Preventing Measures to Control Ich

  • Always maintain good water quality and do regular water changes, because bad quality water makes your fish susceptible to disease like ich;
  • The tank water temperature should be maintained between 75 and 80 °F (24 and 27° C);
  • Quarantine new plants for 5-7 days before adding them to the aquarium. In this case, you can bathe the plants in potassium permanganate;
  • Never use the same equipment for multiple tanks;
  • Never use any pet store water in your aquarium;
  • Overstocking should be avoided;
  • Buy your fish from well known and renowned pet shops. Do not buy fish from the pet fish store that contains diseased tank-mates;
  • Always quarantine new fish for up to 21 days and observe for any signs of illness before adding into the aquarium;
  • Use separate net for multiple tanks to prevent ich;
  • Do not add any fish to the aquarium when nitrite and ammonia levels above zero;
  • Always provide a nutrient-rich and balanced diet to your fish;

Also Read: Rainbow shark: Epalzeorhynchos frenatum

Final Thoughts

Ich is a contagious disease of freshwater aquarium fishes which is caused by the ciliated protozoan parasite ‘Ichthyophthirius multifiliis’. They can kill lots of fish within a short time. To control ich, proper diagnosis and treatment are essential. In this case, you should take preventive measures to avoid fish mortalities. As a preventive measure, salt or high temperature plays an important role to control ich. Therefore, always constant water temperature (75-80 °F or 24-27°C) should be maintained to prevent the growth of ich. When salt or high temperature does not work well to stop the ich outbreak, it is recommended to use medication.

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