How to Treat Ich 101: Diagnosis and Treatment Guide

Feautured Image - freshwater ich
Feautured Image – freshwater ich
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: July 9, 2024
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You might be surprised if you observe strange white spots on your fish, especially if it’s a problem you haven’t faced before.

It might be a symptom of ich, but what is ich? what causes it? Is it harmful? Can it be treated? We’ll go through each of those questions in this guide on how to treat ich. 

Article Summary

  • Ich, also known as “ick,” is a common disease among freshwater fish caused by the parasite Ichthyophthirius multifiliis.
  • Treatment options for ich include raising the water temperature, using salt, water changes, and specific ich medications.
  • Prevention measures for ich include quarantining new fish, disinfecting aquarium equipment, and maintaining optimal tank conditions and water parameters.

What is ich or ick?

Ichthyophthirius multifiliis by Andy Goodwin(USFWS)
Ichthyophthirius multifiliis by Andy Goodwin(USFWS)

Ich or Ick is the same, it both stands for Ichthyophthiriasis that causes Ichthyophthirius multifiliis in freshwater fish. Ich is a very common disease among fish

Freshwater ich vs Saltwater Ich

These are two different types of ich protozoa, freshwater ich is Ichthyophthirius multifiliis while saltwater ich is Cryptocaryon irritans. They also differ in terms of treatment and life cycle.

Does my fish have ich?

The most obvious sign of ich is the small white spots appearing all over the fish’s body. You can also notice them trying to scratch their body by rubbing themselves against the tank. Always try to verify the symptoms before proceeding with treatment.

What looks like Ich But isn’t?

The disease which is often mistaken as ich is called velvet. They are often mistaken for one another due to the similarity of their symptoms which form white dots on fish skin.

Ich can cause cysts to form on the skin surface which can look as white spots spread all over the body while velvet forms smaller cysts on the skin surface but are more numerous and less spread out when compared to ich.

Is Ich Lethal To Fish?

Yes, ich can be fatal to fish and can cause death when left untreated. Usually freshwater fish that are infected by ich already possess a weakened immune system. The various symptoms associated with ich will worsen as the disease progresses. Infected fish will not able to survive ich without proper treatment, it’s best to treat the ich parasite as soon as symptoms are seen.

Freshwater Ich Symptoms

  • White Spots
  • Scratching or fish rubbing against the tank or tank objects
  • Hiding
  • Swimming to the surface
  • Sudden Death


  • Compromised immune system
  • Addition of new fish
  • Infected decor or equipment

Can I treat Ich at home?

Yes, ich can be treated at your own home. Depending on the severity or your preference the treatment can vary but it can certainly be done at home. There are various treatments used to treat ich, like isolation, water changes, utilizing salt, increasing water temperature and using ich medications.

How long does it take for ick to clear up?

Depending on the stage and severity, it could take anywhere from a few days to a few weeks of treatment for ich to be treated.

What is the fastest way to cure Ich?

The fastest and safest way to cure ich in freshwater fish is by raising the water temperature.

How to treat freshwater ich

Clown Loach with Ich
Clown Loach with Ich

There are various ways to treat freshwater fish ich, the key to eliminating ich is by being familiar with its life cycle so you can apply the appropriate treatment. When dealing with ich, its best to approach it as not just treating a single fish but your treating your whole aquarium.

Before proceeding with treating ich parasite, consider what kind of inhabitants your tank has, as certain types of treatment can be harmful. For an example, salt treatment can be harmful to specific types of tank inhabitants such as plants, scaleless fish, or invertebrates.

Treating Ich With Temperature

Raising the water temperature high enough can kill ich or prevent the reproduction of ich. The temperature that prevents reproduction of ich starts at 85°F but that might vary depending on the strain of ich. There are cases where ich was able to resist up 92°F of water temperature.

When doing this procedure, keep in mind that raising the temperature too high can also cause harm to the inhabitants of the tank.

1. Move your fish to a quarantine tank

To proceed with this treatment, the first thing you should do is move the tank inhabitants to a treatment or quarantine tank. This is ideal if you have plants or different types of fish in your tank that can be affected by higher temperatures. If not you can proceed with this treatment in your display tank.

2. Raise the temperature of the aquarium

Raise the temperature of the fish tank to 80 – 85°F depending on what your freshwater fish can tolerate. The tank water temperature must be increased gradually to avoid shock, increase the temp by 2°F every twelve hours until you reach the desired temperature.

If the temperature is not increased up to 85 or higher it will not kill ich but it will help speed up its life cycle which can bring it up to a stage where it can be affected by medication faster. The temperature in the tank needs to be at least 80°F in order for the ich life cycle to continue.

3. Observe

Monitor your fish for any signs of changes. The temperature range must be maintained for at least two weeks or up to a month. If you moved the fish in a quarantine tank, you can increase the temperature in the display tank to 96°F to kill the ich there.

To ensure that ich will be eliminated, this type of treatment is best done with another type of treatment like using salt or medication.

Treating Ich With Salt

Sea Salt
Sea Salt

Salt kills ich through dehydration. The increased salinity of water sucks the water out of ich causing it to dry up. The salt in water can also cause fish to produce more of its slime coat that helps block microorganisms trying to enter its body. While doing this treatment the temperature of the tank must be maintained by at least 80°F so that the life cycle of ich will continue.

Adding aquarium salt

Salt has the ability to kill ich, but before adding it to your infected tank, you should consider the following; the type of salt that you will use, the type of the freshwater fish you have, the size of your fish tank, and other tank inhabitants.

For this process you can use aquarium salt, rock salt, or kosher salt. Using regular table salt that contains iodine can have negative effects to the tank inhabitants, it’s best to use salt without any additives. The fish type and tank size will also influence how much salt you need to use. Be careful when using this method on display tanks with plants, scaleless fish, invertebrates, or other creatures that are sensitive to salinity changes.

Applying Salt

1st Round1tsp. per 3 gallons of water
2nd Round1tsp. per 2 gallons of water
3rd Round1tsp. per 1 gallons of water

To start this ich treatment, try using 1 tsp. of salt per 3 gallons of water then observe if its having any effect on the aquarium fish by up to a week. If you notice positive results, make sure to continue it until there are no signs of ich left. If its doesn’t show any positive results, you might need to increase the salt dose.

When trying to calculate the amount of salt you’re going to use, you also need to consider the decorations inside your tank. Decorations can displace a considerable amount of water making the tank appear full.


You can apply the salt by directly putting it in the tank, but its better to add salt by dissolving it in aquarium water on a separate container then adding it to the water.

Salt Level

Too much salt can harm your tank inhabitants, so it’s important to keep track of how much salt is remaining in your tank. Salt does not evaporate, it will remain in your tank as long as the water is not replaced. Keep a record of every time you add salt or do water changes.

Maintaining Salt Level

Every time you do a water change, you need add an equivalent amount of salt that is removed from the water. To give an example, let’s assume that you have a 20 gallon tank. If you’re going to put 1 tsp. of salt per 2 gallons of water of you’ll end up with a total of 10 tsp. of salt in your tank. Every time you do a water change and remove 20% of water which is 4 gallons of water, you’re going to need to add 2 tsp. of salt back to the tank.

Treating Ich with Medication

Ich Medicine
Ich Medicine

Ich can also be treated by using ich medications. Before applying, make sure to read the instructions included in the medication properly. Be cautious of the inhabitants of the tank before applying the medicine, because it can have negative effects on species such as loaches, snails, and shrimps.

1. Remove any carbon filter media

Before starting with the treatment remove any carbon in the filter as it can hinder with ich medication.

2. Add ich medication to the water

Depending on what type of your medication you’re gonna use, follow the instructions provided.

Treating secondary infections

Ich can leave small wounds on the fish’s body. After any ich treatment, make sure to monitor your aquarium fish and treat them accordingly if their residual wounds develop other bacterial or fungal infection.

Freshwater Ich life cycle

Freshwater Ich Life Cycle
Freshwater Ich Life Cycle

Trophont/Feeding Stage

The first stage of the ich parasite is the trophont/feeding stage where the parasite forms under the fish’s skin, destroying the surrounding cells.

The trophont feeds off the body fluids and dead cells of the fish for several days, growing rapidly during the process.

At this phase in the life cycle of ich parasites, medication and treatment is ineffective.

Tomont/Reproductive Stage

Once the trophont has matured and grown in size, it will fall off its host in order to find an object in the aquarium to attach itself to.

After attaching to a surface, the trophont creates a “cocoon” around its body.

The trophont is now referred to as a tomont, and will multiply quickly by dividing itself. This phase is also immune to treatment.

Theront/Free-swimming Stage

The tomont can produce almost one thousand new parasites (tomites).

Within a couple of days, the tomites will break out of their “cocoons” and become free-swimming ich (now called theronts) to seek out new hosts, causing the entire process to repeat again.

Theronts can survive for roughly 1 to 2 days in a fish tank without finding a host. This is also the stage when medication is at its most effectiveness.

How to prevent freshwater ich?

Quarantine New Fish

Before you add new fish to your aquarium, make sure to quarantine and disinfect them as they might have ich or other diseases. You can put new fish in a quarantine tank for two weeks up to a month and monitor for any symptoms. The temperature of the quarantine tank must be maintained at 75-79°F so that the life cycle of freshwater ich will continue.

Disinfecting Aquarium Plants, Decorations, Tools, and Equipment

Another way to prevent ich is by disinfecting any object or equipment before you use or put it in your aquarium. This applies to all equipment even the ones from your other tanks.

Maintain tank condition and water parameters.

Having healthy fish is a way to prevent an ich outbreak. This is done by maintaining proper tank condition and optimal water parameters.


How did my fish get ick?

The usual cause of ich is a weakened immune system due to stress. Fish getting stressed can be caused by contamination, poor water quality, temperature variation, and other factors

Can Ich Affect Humans?

Ich doesn’t affect humans. But be cautious when handling infected fish as you can pass the disease to other fish and aquariums. Make sure to properly wash your hands every time you’re exposed to infected fish. Proper disinfection also applies to any aquariums tools that you used.

Why does only one of my fish have Ich?

You might think that only one of your fish has ich, but if one of your freshwater fish is exhibiting symptoms it’s best to assume that the whole tank is infected. 

What temp kills ich?

There’s no exact temperature where ich dies because it varies from strain to strain. But the temperature range which affects the capability of ich to reproduce is around 85°F above.

Does Ich go away on its own?

There’s a possibility of fish being healthy enough to fight off ich or develop a resistance to it. But the downside of not treating ich is that it will remain in your tank just waiting for another aquarium fish to become weak to infect it. It’s much better to treat ich as soon as you notice any symptoms.


Thanks for reading! I hope this guide on how to treat ich was helpful. If you enjoyed this article, feel free to browse the site for more aquarium guides and product reviews.

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