Marine Ich 101: Marine Ich Treat Guide (2024)

Featured Image - marine ich
Featured Image – marine ich
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: July 9, 2024
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Did you observe peculiar white spots on your saltwater fish? This could indicate the presence of marine ich. Characterized by noticeable white patches on the fish’s body, marine ich is a common ailment in saltwater fish. Without timely treatment, the disease can spread quickly and may result in death. Our guide provides essential information on how to effectively combat marine ich.

Article Summary

  • Marine Ich, caused by a protozoan parasite called Cryptocaryon irritans, is a common disease among saltwater fish characterized by the appearance of white spots on their bodies.
  • It is important to note that Marine Ich is different from freshwater Ich and requires different treatment methods.
  • To treat Marine Ich, move infected fish to a treatment tank, use copper-based medications, monitor copper levels, maintain proper water parameters, apply medication during the parasite’s active hours, and observe for at least 30 days followed by an observation period of 2 weeks or more.

What is Marine Ich or Saltwater Ich?

Cryptocaryon irritans
Cryptocaryon irritans by Fedtred

Marine ich or also known as marine white spot disease is a disease caused by a protozoan parasite called Cryptocaryon irritans. This condition affects saltwater fish.

Marine ich is different from freshwater ich which is caused by Ichthyophthirius multifiliis. It’s important to remember that the method of treating ich in freshwater differs from that used in marine environments.

But these two ich parasites are similar in a way that they both go through a life cycle and are vulnerable to medication at a certain point of this cycle.

Where Does Marine Ich/Saltwater Ich Come From?

Marine Ich or Saltwater Ich is present in different bodies of water. They are present in the wild, distributor tanks, pet store tanks, and even in your own home saltwater aquarium or reef aquarium.

What Causes Marine Ich?

Saltwater Ich is commonly believed to be caused by stress. But that’s only partly true. Saltwater fish can get prone to an ich outbreak due to weakened immune system caused by stress and not because of stress itself. It is believed that ich is always present in water. So once your aquarium fish gets stressed, there’s a chance for them to develop ich.

Knowing Marine Ich

Like any other fish diseases, getting to know saltwater ich, its symptoms, and how it affects your fish is vital when it comes to proper treatment. Before we proceed with the treatment steps, let’s get you familiar with marine or saltwater ich first.

What Does Marine Ich Look Like?

Before you cure ich, you must first be familiar with its appearance. Ich is commonly mistaken for marine velvet disease or vice versa due to both of them having white spots as a sign.

Marine velvet white spots are numerous and can somehow be compared to the appearance of sugar coating. Whereas saltwater ich looks like small white spots that are sparsely spread all over a fish’s body. But sometimes, there are instances where the spots are as visible because they are only present on the gills of the infected aquarium fish.

See the short clip below to see the differences.

Fish Velvet vs Ich

Symptoms of Marine Ich

Being familiar with the symptoms of a saltwater ich outbreak can help with the treatment. Aside from the white spots that can appear on the infected fish’s body, there are other symptoms that you should watch out for.

Watch out for the following symptoms:

  • Raised white spots on the skin that resemble grains of salt
  • Poor appetite
  • Listlessness
  • Clamped fins
  • Fading body colors
  • Rapid gill movement
  • Dashing and scratching against objects

Life Cycle Of Marine Ich

The saltwater ich has a 4 stage life cycle. Being familiar with this cycle is the key to treating ich. The free moving stage or theron stage is the time when the cryptocaryon irritans parasite is vulnerable. 


Treating the parasites in this first stage isn’t very effective as they’re protected under your fish’s skin. This is also the stage where they appear as white spots on the skin of your fish. During this time, they feed on the cells and fluids of your saltwater fish until they are ready to go to the next stage.


The second stage is when the trophants have finished feeding and leave your fish’s body as a protomant. The parasites lose their ability to swim and will fall to the bottom of the fish tank. In around three hours, they become a tomont and develop into a hardened cyst that will soon hatch.


One the parasite falls off the marine fish it will become a cyst. Inside the cyst are hundreds of new parasites called tomites.

After a few days (sometimes weeks), the cyst breaks open and releases free-swimming theronts that are in search of a host.


During this stage is when saltwater ich is most sensitive to medication.

This stage can be considered as the infection period, this is also the stage where the disease is vulnerable and prone to treatment.

The theronts have about 6 hours to find a body (host) to attach to. Once they locate one, they will burrow into your fish’s skin and become a trophont and the whole cycle repeats itself. This cycle will repeat until the infected fish gets treated or the fish fights off the infection.

How To Treat Marine Ich

Seachem Cupramine
Seachem Cupramine

Treating Marine Ich

There are different approaches to treating saltwater ich. Depending on your setup and the number of marine fish you have. When trying to treat or eradicate ich, you should think of your whole aquarium having the saltwater ich parasite not just your fish.

The most common way is moving infected fish to a treatment tank or quarantine tank and using copper to treat the fish. Treatment is usually done like this because it leaves the parasite without the host in the original tank while the parasites on your marine fish get treated in the other tank.

This approach is also done on reef tanks as copper medication can have harmful effects to corals.

Therapeutic Range

Another important thing to know during the treatment process is the therapeutic range of the type of copper you’re gonna be using. Make sure to test the water parameters daily during copper treatment as exceeding the copper range can be detrimental to fish health.

It will also be helpful to always check the user manual of the copper medication you’re gonna use to be sure of the therapeutic range.

Using Bare Bottom Tanks

The reason why saltwater ich is best treated at bare bottom tanks without decoration is so that the water parameters are easier to maintain. Having decorations or rocks can cause changes to the copper levels due to their ability to absorb the copper.

Treating Marine Ich Using Copper

Copper treatments are effective during the theront stage of salwater ich. You can use either chelated copper or copper sulfate type of medication.

  1. The first step is to prepare a hospital tank that has the same parameters as your display tank and other things you’re gonna use such as medications, aquarium fish nets, gloves, and testers for copper, ammonia, nitrate, and nitrite.
  2. The next step is to move your fish into the hospital tank. Make sure that the hospital tank matches the water parameters of your display tank.
  3. Apply the copper medication to the water, the copper level should be increased incrementally in the span of 2-3 days, this will give your fish time to adjust and give you time to monitor them for any adverse reaction. It is advisable to apply medicine during fish resting hours when the parasite is active, this is usually around 12 midnight to 7am. 
  4. Once you reach the therapeutic range required, you’re gonna need to maintain it for at least 30 days. Make sure to check your fish’s conditions daily during the treatment period. Exceeding the therapeutic range can be harmful to your fish and corals, so make sure that you just maintain a healthy range.
  5. Aside from the copper level, make sure to check the ammonia, nitrate, and nitrate levels. You might need to do water changes if the water parameters are not optimal. Another thing to maintain is the temperature at 77°F – 80°F, this is so that the life cycle of the parasite will still continue.
  6. After the 30 days of treatment, continue to observe your fish for 2 weeks or more for signs of saltwater ich or sickness.
  7. Your display tank will be in fallow during the treatment period but still make sure to maintain the water parameters and temperature for 6 weeks or up to 8 weeks. This is to make sure that the parasite life cycle will proceed. The parasite will die off if the cycle proceeds without a host.

The video below can help you more with the process.

Marine Ich Treatment Products

Copper Medications

There are different types of copper medications to treat saltwater ich, here are the ones that are commonly used. For beginners, it is safer to use copper chelate medication like Copper Power because it has a higher margin of error which is between 2.0 to 2.5 PPM, unlike other copper medications which can range from 0.05 to 0.08 PPM.

If you’re gonna use copper medications, make sure to remove carbon based filter media on your tank. Carbon has the ability to remove the copper present in the tank.

  • Copper Power
  • Coppersafe
  • Seachem Cupramine 
  • Brightwell Aquatics Cuprion


Aside from medications, you’re also gonna need other tools such as a water testing kits and a quarantine tank.

  • Copper Levels Checker
  • Fish Catch Net
  • Ammonia Alert

Marine Ich Prevention

Saltwater Aquarium
Saltwater Aquarium

They say that prevention is always better than the cure. There are different ways to prevent ich outbreaks in saltwater aquariums. Here are some prevention steps that you can do:


The best way to prevent saltwater ich is good quarantine practice. You should always assume that any new fish or creature is infected with ich. So make sure to properly quarantine any fish you’re going to introduce to your saltwater aquarium. Put them in a separate tank for a month and transfer them back afterwards if they don’t exhibit any symptoms.


You could also pre-treat new fish with copper but this can be lethal if not administered properly.

Don’t Share Equipment

Similar to introducing a new fish to your saltwater fish tank, the same can be said with fish tank equipment. Always be mindful when using equipment for different tanks. It’s best to have different equipment for each tank, especially when it comes to equipment used for quarantine tanks.

Equipment that are used on quarantine tanks, especially those medicated with copper, should not be used on your other tanks. Aside from the risk of infection there is also a risk of harming other fish due to the leftover copper.

Tank Placement

Don’t place your tanks too close together. It should be at least 10 feet away or more. The reason for this is infected tanks can spread the parasite to nearby aquariums due to water splashes or sprays due to movement or filters.


Having a fish that is infected with ich can be worrying because it can be lethal and tricky to treat. Being familiar with saltwater ich and its life cycle can help you facilitate the treatment effectively and increase the survival chance of sick fish in your saltwater or reef aquarium.

Thanks for reading, I hope that this guide was helpful. Feel free to share this with your friends and fellow aquarists to help them cure ich.

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