A Guide To Understanding Fish Ich And Ways To Prevent It

fish ich

You need to have a great amount of patience in maintaining an aquarium at home. Fishes and other aquatic animals demand proper care and attention. So, you need to always remember this before keeping them at home. Also, fishes are prone to diseases, and they may occur anytime without your notice.

If infected, you can choose to quarantine fishes before introducing them to your display tank. However, this is not possible all the time. Still, you cannot rule out the possibility of common diseases. There are several effective treatments for fish ich. They can result in complications if not administered appropriately. This article will explain what exactly fish ich disease is, what causes it, and how to cure Ich on fish.

To know more about different Saltwater and Freshwater Aquarium Fish Diseases, click this article “Aquarium Fish Diseases: Causes, Symptoms, and Treatments“.

What is Fish ich? 

Ich is one of the most persistent and common diseases seen in fishes. Usually, you will notice white nodules on gills, fins, and body whenever a fish is suffering from the condition. Hence, fish ich is also known as White Spot Disease. The nodules seem like white grains of salt. And, the spot is nothing but an encysted parasite. The microbe responsible for fish ich is an ectoparasite Ichthyophthirius multifiliis, and it usually affects freshwater fishes.

Ichthyophthirius multifiliis can easily gain entry into a home aquarium or a fish pond. It can be through a new fish or any equipment. Once a microorganism gains entry into a large fish culture facility, it becomes difficult to control the growth of the parasite. This is because of its unique life stages and reproductive cycle. If you fail to take appropriate measures for controlling Ich, then it can prove to be fatal.

The parasite damages the skin and gills once it enters the tissues. This leads to loss of skin and ulceration. Eventually, severe infections result in death. Also, the respiratory system gets affected when there is damage to the gills. Hence, the rate of oxygen intake from water is reduced. This also results in the fish becoming less tolerant of low concentrations of oxygen in the water when suffering from fish ich. 

What causes Ich in fish?

The parasite responsible for Ich, Ichthyophthirius multifiliis is quite widespread. Experts believe that it is present in most of the aquariums, holding tanks and in fish rearing and breeding ponds. An aquarium fish is bound to come in contact with this parasite several times. As it is widespread, most of the freshwater fishes develop a good immune response against the condition caused by the parasite. Captive fishes fall prey to fish Ich as their immune system is not functioning at optimum levels. As a result, they have to cope with stress at various stages. This further lowers their immune response. Therefore, your fishes are more susceptible to Ich.

Several factors contribute to stress in a fish’s life. It can be fluctuations in water temperature, quality of water, improper diet, and due to tank inhabitants. One of the most severe causes of stress in a fish is shipping and handling. Hence, moving from a fish breeding pond to a retailer and then finally to your home aquarium can be extremely stressful for a fish. 

Life stages of the ectoparasite 

The parasite Ichthyophthirius multifiliis goes through the following life stages. The life cycle depends on the temperature of water in the aquarium. At 25ºC, the entire lifecycle takes seven days. It is for eight weeks when the temperature is 6ºC.

Feeding Stage – Active stage in the life of the parasite referred to as Trophozoites
– Feeds in a nodule formed in gill epithelium or the skin
Encapsulated Dividing Stage – Trophont (a mature trophozoite) falls after feeding itself
– Attaches itself to an ornamental object, gravel, nets or plants in an aquarium – Divides 10x by binary fission resulting in infectious theronts
Production and release of Tomites – Trophont bursts to release Tomites
– They penetrate the skin of fish and the cycle repeats

How does an ectoparasite multiply? 

If you want to understand how fish get Ich, then you must first understand how ectoparasite survives and multiply. The life cycle of the parasite is quite difficult to understand. Once it has attached itself to the body of a fish, it starts feeding on the tissues resulting in irritation. The fish does try to get rid of the parasite in the process. The parasite moves around in the cyst while feeding and growing. The encapsulation makes it difficult to treat Ich as medications cannot penetrate through the wall of cyst for destroying the parasite. The parasite is referred to as Trophozoite during this stage.

A mature trophozoite is called a Trophont. It bursts through the wall of the cyst. The Trophonts then start multiplying at a rapid pace. They release tomites during the process, which are nothing but the ich-infecting units. This step is dependent entirely on the temperature. Warmer temperatures signify faster replications. The tomites swim around looking for the body of a fish to attach to. Once they find the fish, the cycle continues. 

Most of the medications available today kill the tomites for stopping the cycle of the parasite in your tank. The tomites can survive only for 48 hours if they cannot attach themselves to the body of a fish. Hence, the best way to control Ich is by killing them during this stage. They also get attached to gravel, filter material, and plants.

Symptoms of Fish Ich Disease

It is not difficult to identify Ich in fishes. The symptoms are quite evident. You can find white spots mainly on the gills and the body. As a result, the fish becomes irritated. As the condition worsens, the fish may try to rub its body against the bottom of the tank or the sides. The disease results in severe agitation, respiratory distress, loss of appetite, and, eventually, death. 

Here are some of the common signs and symptoms that you should take seriously.  

Behavioral Changes

If you notice any change in the behavioral pattern of your fish, then you need to take the situation seriously. The typical behaviors noted in an infected fish include rapid breathing, resting on the bottom, anorexia, scratching or rubbing against objects, hiding abnormally, or upside-down swimming near the surface. These signs do not show in any sub-clinically infected fish. A healthy fish which has a recently attached parasite will not start showing these symptoms. Moreover, it will become evident only when the parasite has fed on the fish. 

Changes in skin

You will be able to spot visible lesions on the skin in the form of white spots. These spots are nothing but trophonts that feed on tissues.

Gill infection

Any infection to gills would result in fast respiration or breathing at the surface. In addition, there will be a slowdown in breathing and their activity. Further, the slowdown in breathing can cause them to rest on gravel or sand. A careful examination can reveal white spots in the region. Also, a biopsy can reveal the trophonts.

How to cure Ich on fish? 

As the lifecycle of the parasite Ichthyophthirius multifiliis is temperature-sensitive, the temperature has to be increased to speed up the formation of tomites. You can complete the treatment in four days if you maintain the appropriate temperature and then kill the tomites. For instance, if the temperature of the water is low, then you will have to wait for weeks.

There is no specific best treatment for Ich on fish. We cannot kill Ich when it has attached itself to the body of a fish. As a result, moving the infected fish to a quarantine tank is not going to be beneficial. Hence, if any fish in your tank has Ich, you need to understand that the entire system is contaminated. You need to look at other ways to tackle the condition. 

You can consider removing all the fishes out of a tank as tomites can survive for 48 hours if they do not attach themselves to the body of a fish. Any existing parasite should be dead within two days. You can wait for four days before transferring your fishes to your aquarium tank again. You need to remember that you are treating the tank and not the fish in this process. So, make sure to follow the best measures to control fish ich. 

Treating fish ich with salt is a popular remedy followed by most of the fish lovers. You can check out this YouTube video to follow the steps accurately. 

The best treatment for Ich on fish 

Total Fish Removal – Tomites that release from the Trophont need the body of a fish within 48 hours to survive
– With no host body to attach to, tomites will die within 48 hours
– Maintaining a temperature of 80 degrees Fahrenheit will kill them in 2 days in the absence of a fish
Heat Treatment – Is highly effective and be combined with other treatments
– Can be used on fishes that can tolerate high temperatures
– Unsuitable for goldfish and koi
– Accelerates the life cycle of parasite thereby allowing other treatments to take effect sooner
Treating ich with salt   – Aquarium salt can treat mild infections
– Add 3-5 grams per liter for two weeks
– Catfishes are sensitive to salt. Hence, this method is not suitable for them.
– Continued use of salt develops parasite’s resistance to salt
Chemical Treatment – Involves the use of Malachite green, Formalin, Chelated copper, Potassium permanganate, Methylene Blue and Quinine
– There are specific chemical solutions available in the market to treat Ich  
– Effective only against tomites Precautions to take
– Needs to be used carefully to avoid eye contact and to prevent inhalation
– Removes oxygen from water and can damage the gills of a fish
– Formalin is toxic in soft water
Treatment with Copper – Effective treatment for parasite
– Recommended dosage: 0.15-0.3 mg/L Precautions
– Copper is more toxic to fish in soft water
– Toxic to other invertebrates including snails and shrimp

Ways to prevent fish Ich

Your topmost priority should be to prevent the infection entirely. This can be done by avoiding the introduction of the parasite into the aquarium tank. You should quarantine new tropical fish for a minimum of four weeks. Also, make sure to wash your hands before treating the tank. Use separate and clean equipment to lower the chances of spreading the parasites. 

Wash plants in lukewarm water before placing them in the tank. Also, treat the plants with any disinfectant or by using any antiparasite remedies. Ich cannot be prevented with vaccinations. Hence, it is best to stick to preventative measures. 

Here are some other ich prevention tips that you can consider.

  • Purchases only healthy fishes
  • Never buy any fish from a tank that has a dead fish
  • New fishes should be appropriately quarantined for a minimum of two weeks 
  • Never purchase plants that have been placed in a fish tank before
  • Purchase fish from a direct source to prevent handling stress
  • Avoid fluctuations in ammonia levels, pH and temperature
  • Never overstock your tank
  • Maintain excellent water quality 

Using commercial medications 

There are numerous proven products available in the market that can help you deal with fish Ich in your pet fishes. Hence, these solutions are opted by a lot of people who keep fishes in their homes. 

Here are some of the most popular offerings that you can consider.

Garlic-based medications

This is a great medication for fishes that are showing signs of anorexia. The smell of garlic will enhance the diet naturally. As a result, they will be compelled to eat. Thera A is a popular anti-parasitic and non-medicated formula that will provide a healthy dose of garlic to your tank inhabitants. This is not prescribed medication for fish ich. But, it can still prove to be beneficial in treating the associated symptoms. 

Kordon Rid Ich

Kordon Rid Ich is one of the most popular Ich medicines for fish available in the market. It consists of a potent form of formalin. This component can help significantly in controlling parasites responsible for fish ich. Excess of formalin can prove to be toxic for your fishes. Hence, you need to remember that this makes it is both deadly as well as a powerful antiparasite.

Moreover, you should take proper care while using the dosage. Also, make sure to check the dosage prescribed by the manufacturers. It is best to use medications that spare your fishes but kill the parasites while treating Ich.  


Para Guard is a preferable medication for treating fish ich and is less toxic. Mainly, it consists of an aldehyde. The downside is that it has not been formulated for treating Ich fish disease exclusively. However, it does try to eradicate any ectoparasite present on fishes efficiently and effectively. Above all, it is a synergistic blend of fish protective polymers and malachite green that are safe. 


Precautionary measures are always beneficial in avoiding the condition altogether. Upon spotting symptoms, you can take necessary actions once you are aware of what causes Ich in fish. The last resort should be turning to medications. You should focus on trying all possible steps to stop the entry of parasite into your aquarium tank. Hence, you should act if you notice any signs, such as behavioral changes. 

To know more about different Saltwater and Freshwater Aquarium Fish Diseases, click this article “Aquarium Fish Diseases: Causes, Symptoms, and Treatments“.