Saltwater Ich – All The Facts to Save Your Fish

What is Saltwater Ich?

Saltwater Ich is a common, yet devastating affliction that is caused by ocean parasites called Cryptocaryon Irritans. Marine Ich and White Spot Disease are some other names that it’s known by, but it is all the same pesky microscopic parasite.


Cryptocaryon Irritans’ sounds scary, but they are basically like fleas that feed on your fish. Just like the fleas that can infest a dog or cat, Saltwater Ich can be really difficult to completely eradicate from an environment.


Saltwater Ich is often confused with Marine Velvet, which is a similar parasitic based infection. Marine Velvet is caused by the Amyloodinium parasite, but symptoms and treatments are similar. The main difference is that Marine Velvet primarily attacks the grills and lungs of the fish, making it far more deadly. Marine Velvet also has a wider and less pronounced white patch than Ich.

Where Does Saltwater Ich Come From?

The Cryptocaryon parasites are present in most home aquariums, Local Fish Stores (LFS) and fish wholesalers. It is not caused by stress, but stress is a big risk factor that can cause an aquarium with a slight Saltwater Ich issue to turn into an active outbreak.


These microscopic parasites are almost always present in the water of wild caught fish and are easily transmitted on anything wet.  This causes Saltwater Ich to exist in the holding tanks of fish wholesalers and distributors.  The parasites will then make their way to your local pet store and from there they will enter your home aquarium.


Powder Brown Tang with an advanced case of Saltwater Ich

Quarantining all deliveries of fish with an observation period or preventive medicine treatment could mitigate the risk of Saltwater Ich outbreaks. However, this rarely happens due to the limited space and profit margins of many businesses that sell livestock.

Even if every wholesaler guaranteed 100% Saltwater Ich free livestock, it would only take one mistake in the supply chain to reintroduce the parasites. A single second of accidentally cross-contaminating with a questionable net or unwashed hands will undo any preventive measure that was taken. This is why you should always assume that any tank water you come in contact with is contaminated with Cryptocaryon Irritans and other parasites.

Saltwater Fish Ich Symptoms

Healthy Fish can normally stave off the effects of Saltwater Ich and won’t show any signs of infection. However, this can quickly change if stress or poor water quality compromises the animal’s immune system.


Saltwater Ich presents itself as small white spots that can exponentially multiply to cover most of the fish. These patchy white spots can appear on the fins, body or gills of your fish.


Your fish may also exhibit a behavior known as flashing. Flashing is the term used to describe when a fish scratches itself against the sand or rocks. Abnormal swimming patterns, cloudy eyes and loss of appetite may also be early warning signs of Marine Ich.

Saltwater Ich Life Cycle

Saltwater Ich has a fairly complex 4 stage life cycle that makes treating it difficult. The parasites are only vulnerable to treatment when they are free swimming. If any parasites fail to reach this stage before the end of the treatment, they will survive to reinfect the fish.


Life Cycle of Cryptocaryon irritans - Credit: Colorni and Burgess
  1. Trophont – This is the stage where the parasite appears as those white patches on an infected fish. During this feeding stage, the parasite will embed itself into the flesh of the fish until it has fed enough to proceed to the next stage of its life cycle.
  2. Protomont – After feeding on a fish for 2-10 days the parasite will fall off and sit on the bottom of your aquarium in preparation for the next stage. The Protomont can be compared to the way a Deer Tick will drop off an animal after drinking its fill of blood.
  3. Tomont – Once the Protomont has fallen off the fish, it will attach itself to the aquarium substrate within 8 hours. During the Tomont stage, the parasite will divide itself to form up to 1000 child cells, known as Tomites. These Tomites will be released as the final stage of the Saltwater Ich parasite. The Tomont can reproduce for up to 72 days before releasing free swimming parasites.
  4. Theronts – The parasite is free swimming and can survive for up to 8 hours in open water. It will actively look for a fish to feed on in an attempt to restart the life cycle. Ich has evolved to begin its infectious stage at night when most fish are resting, as this increases the odds of finding a host. The cycle will continue until the host fish is able to fend off the infection or dies from Saltwater Ich complications.

Saltwater Ich Treatment Options

There are countless Saltwater Ich “treatments” that I would classify as myths. These practices are either highly ineffective or outright harmful for the fish. Garlic and other food supplements may help to boost the immune system of a fish, but the various dip based methods normally cause more stress that further weakens your fish.


There is no reef safe treatment for Saltwater Ich. Treatments that kill the parasites will also kill all of your coral, snails, shrimp and any other invertebrates.


Never reuse any equipment that was exposed to copper in your display tank. You may accidentally introduce lethal levels of copper to the system.


The two most proven and effective treatments for Marine Ich are Chloroquine Phosphate and Copper Sulfate based medications. CP or pharmaceutical grade Chloroquine Phosphate requires a prescription from a veterinarian, so this leads most hobbyists to use copper treatments. The CP that is available online from eBay and other websites is rarely medical grade and not worth the risk to your fish.


Copper Based Saltwater Ich Treatment


Copper is a poison and has been compared to chemotherapy for fish. It is often deadly to fish at unregulated levels or if a fish is too weak when the treatment begins. Purchasing a reliable copper test kit is absolutely required if you intend to use any copper medications on your fish.

I recommend the Salifert copper test kit or the Seachem copper that are both available on Amazon or at your LFS. 


The API copper test kits are inaccurate and should be avoided unless you are specifically directed to use it for certain types of copper. The manufacturer of the copper treatment will have the most current information and test kit recommendation for their product.


Test kits are a necessity because copper must be maintained at a specific concentration in the treatment tank. The concentration differs from product to product and is referred to as the therapeutic level. You must constantly maintain the correct therapeutic level of copper for the duration of the treatment. Sustaining lower than the therapeutic level will allow Saltwater Ich to survive treatment, but exceeding the therapeutic level of copper can be fatal to your fish.


Copper will only kill the saltwater ich parasites in the free swimming stage while they are searching for a host. Because it is not possible to kill Cryptocaryon Irritans during the feeding or reproduction stages your goal is to break the cycle directly after the Tomont stage. This means that the duration of any treatment will vary depending on how long it takes the parasite to become free swimming. The most common duration is 30 days, but some forms of Saltwater Ich can take as long as 72 days to reach the free swimming stage.


Your treatment goal with copper is to effectively play a game of chicken between the parasite and the host fish. Instead of racing cars into a potential head-on collision, they are slowly being exposed to poison until one of them succumbs. That sounds bleak, but I want to highlight the danger of copper treatments to anyone that might not realize it’s actually a poison.


Copper Treatment Recap

  • Copper is a poison that’s deadly to all invertebrates at any concentration. It is also fatal to fish in large dosages or for extended amounts of time.
  • You must use a high-quality test kit for the safety of your fish and the effectiveness of the treatment. Salifert or Seachem copper test kits are recommended for most medications.
  • Copper must be maintained at the therapeutic level for the specific medication you are using. Failing to stay at this level for any amount may cause the treatment to fail.
  • Therapeutic levels must be maintained for as long as it takes for all Saltwater Ich parasites to reach the free swimming life cycle. A single surviving Tomont stage parasite will release enough new parasites to infect your fish again.

Copper treatments come in powder and liquid forms. Powdered copper is notoriously difficult to mix into water and often precipitates out, which has made liquids more popular.

You should always consult the manufacturer of your copper treatment product if you have very specific questions, but this is some general information on some of the common options.


Commonly Used Treatment Products


Cupramine from Seachem is a very popular choice that contains ionic copper. Cupramine has the advantage of mixing much easier into the water than some other products. The Cupramine therapeutic level is 0.50 ppm and should only be read with the Seachem or Salifert copper test kit.

Prime, Amguard or other ammonia binding products should be avoided while using Cupramine because they have been reported to increase the mortality rate of fish during treatment.


Coppersafe is a much older liquid option that contains chelated copper with a therapeutic level between 1.5 – 2.0 ppm. The API test kit is recommended for this treatment and you are able to use ammonia binding products. However, there are reports that it less effective than some other options.


Cuprion from Brightwell Aquatics is another ionic copper liquid-based treatment. The therapeutic level is 0.20 ppm. Seachem or Salifert copper test kit is recommended again for this product and ammonia binders should be avoided.


Copper Power Blue is advertised as the safest treatment for Saltwater Ich. The therapeutic level between 1.5 – 2.0 ppm for Copper Power, but they claim 2.5ppm is also safe. The API test kit is recommended for monitoring this product.


You will want to monitor your fish for another 30 to 90 days after the treatment is completed to play it safe because Saltwater Ich can be very tricky to defeat. Lots of reefers have transferred their fish from the treatment tank to the display tank too quickly and reintroduced the parasite. Most fish will not survive repeated treatments of copper without ample recovery time.

After learning this much about Saltwater Ich, you’re probably realizing that treatment is a grueling process that does not even guarantee success. Prevention is by far the best course of action for anyone with a reef aquarium.


Saltwater Ich Prevention

Any Saltwater Ich outbreak is a traumatic event for the fish and the hobbyist. I highly advise you to take every possible step to prevent these parasites from attacking your fish in the first place.


Even if your fish don’t have any symptoms, your aquarium may still be contaminated with Marine Ich. The parasites will lay in wait until the conditions are optimal for an outbreak. Viewing samples from your substrate and fish biopsies with a high powered microscope is the only way to truly identify the parasites until a fish shows white spots.


Purple Tang with early stage Saltwater Ich infection

100% preventing Saltwater Ich from entering your water is a real challenge. Many of the processes are similar to the protocols of a medical lab that deals with infectious diseases.  Most hobbyists will not be able to follow all of these recommendations, but any efforts to prevent contamination are usually better than none at all.

Prevention Best Practices

  • Quarantine all fish, coral and invertebrates for 45 to 90 days. Only a live fish can host the feeding stage parasite, but the Tomont stage of reproduction can latch onto the shell of a snail or piece of coral.  You can think of snails as potential landmines full of parasites that are primed to explode when your fish approach. Troubling, isn’t it?
  • Never share equipment between aquariums. Saltwater Ich can be transmitted by any wet surface, including your hands.  Nets and other equipment exposed to copper treatment tanks can also contain lethal levels of copper and should only be used for future treatment tanks.
  • Keep quarantine and treatment tanks 10 feet or more away from any other aquariums. Saltwater Ich can also be transmitted by the aerosol spray from filters, skimmers and pumps.
  • Pretreating newly purchased fish with copper has become a popular preventive measure. Sadly, this has also lead to the death of countless otherwise healthy fish.  Dosing errors and the harshness of copper on a fish that is already stressed from travel can greatly decrease the odds of survival for any new fish.  I recommend keeping new fish under observation before deciding if using a copper treatment is the correct choice.
  • While treating all your fish in a separate hospital or quarantine tank you must have a 72-90 day fishless, or fallow period in your display tank. This fallow period should cause any remaining parasite to die off after being unable to find a fish to feed on.  Failing to allow enough time before reintroducing you fish can cause them to be quickly infected again.

Saltwater Ich Conclusion

There are no simple methods for treating or preventing Saltwater Ich in your reef aquarium.  This is why many people simply dump livestock directly into their display tank after saying a prayer or gripping a lucky charm.


Many hobbyists have gotten lucky and never had an outbreak, but it is a bit like playing Russian Roulette with your aquarium and the lives of your pets.


If you have a small tank with a few low-cost fish, it may be worth the risk of rolling the dice each time you add a new piece of coral or cleanup crew member.  But, can you say the same if you have invested 1000’s of dollars into a larger reef tank? What if you have fish that you’re as emotionally attached to like your dog or cat?


I am not here to shame anyone about how they manage the risk of diseases like Saltwater Ich in their aquariums. My goal is to just present you with the facts and inform you of any additional risks that you may not have been aware of.  This is your hobby and the final decision rests on you and you alone.

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Phil Beauregard

Phil Beauregard

A man with a beard, that you can trust! Phil Beauregard is a business consultant and entrepreneur that has been addicted to fish keeping since childhood. He grew up with stories of his grandfather’s exploits during the early days of reef aquariums and African Cichlid breeding. Phil brings a flair for high tech DIY projects and his love of teaching others to the reefing community.

1 thought on “Saltwater Ich – All The Facts to Save Your Fish”

  1. Do you have a Youtube channel as well with this kind of content on it? I would love to see this post turned into a longer video if possible. Maybe I can share on it on my website.

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