Marine Ich (Cryptocaryon Irritants)

What is Marine Ich ???

Marine ich (sometimes call white spot disease) is among the more common viruses in the hobby today.  It can also be one of the more frustrating situations to deal with.  A large part of this frustration happens when people do not completely understanding the life cycle of this virus.  The below diagram shows the life cycle of the ich virus.



The most important thing to understand is that if you have ich in your tank, you will only be able to actual see it during a very small part of its overall life cycle, when its attached to the skin of a fish. Even, then it can be hard to properly identify.  What can further complicate a proper diagnosis is that some fish will have a natural resistance to ich never becoming infected while others in the same tank will be infected but not show any visible signs of the infection.  It is also important to note that early symptoms of ich can easily be mistaken other diseases depending on the exact strain of virus.  Careful observation is the key.

What this means is that when your tank is infected, you can only see symptoms during a very small part of the life cycle, and that your tank is infected even if your fish may be resistant. It will also explain why symptoms come and go.  At times, this has given many hobbyists false belief the ich was gone from their tank only to have it return again.   This also means that in a closed environment, such as an aquarium, ich can reproduce at an incredibly fast rate if you do not take immediate measures to break the life cycle.

It would be important to note the exact length of time the virus stays dormant in the substrate is a topic that can be debated. The expert opinions range from 1 to 3 months.

What can Lead to a Ich Outbreak

Ich symptoms can typically be triggered or worsened by a few key environmental factors / changes in the fish’s environment.  It can be almost anything that adds some prolonged stress to the fish which will allow the virus to take hold.  Examples of these stress triggers are listed below.  Your fish must be exposed to the ich virus in order to catch this disease.  Stress will not cause ich, that will only make the symptoms worse.  Ich would need to introduced into your aquarium by a fish carrying the virus, or anything else being introduced to your aquarium that can carry the virus like: saltwater, live rock…. and so on.

A)     Aggression between fish
B)      Low oxygen levels in the water
C)      Changes in the pH levels or consistently low pH levels,
D)     Changes in water temperature or consistently low temperatures,
E)      Exposure to high levels of ammonia, nitrite, or nitrate,
F)      No hiding spots for fish to retreat to (to make them feel safe again) when they feel threatened.


Signs of the Disease

This can vary due to the exact strain of the virus and the fish’s ability / natural resistance to fight off the disease.  The below are some of the more common symptoms that you can find.

A)     Small white spots, and/or larger white nodules, all over the body (looking a lot like someone put salt on the fish)
B)      A few patches on their fins, skin, or gills were the coloring of the fish seams faded or lighter in color
C)      The overall coloring of the fish looks faded or lighter in color than normal and it stays like that.
D)     Ragged / damaged fins
E)      Cloudy eyes
F)      Pale gills
G)     Changes to the fish’s natural slime coating

Fish infected with ich will not always show visible symptoms of having the virus,  or the virus may only infect the gills.  In these situations there will be changes in the behavior of the fish that will indicate it is infected with ich.  These behavioral symptoms can include:

A)     Flashing or scratching like behavior with short bursts of rapid movement,
B)      Staying near the surface of the tank
C)      Remaining in a hiding spot and not coming out or staying on the bottom of the tank in a area with lower lighting levels
D)     Lethargic or longer periods of inactivity
E)      Rapid breathing or what looks like difficulties breathing
F)      Losing weight and not eating as normal


I’ve got ich in my tank, now what ???

Quick recognition of the virus is key to dealing with the situation and breaking the life cycle of the virus.  If you do not take quick action, the virus can spread at an explosive rate inflecting and possibly killing all the fish in your tank. I would suggest taking the below listed steps,

A)     Remove the infected fish for treatment in a quarantine set-up
B)     Check all water parameters in the main tank and correct for any that are not within the safe zone.
C)     Complete light substrate cleanings once every three days
D)     Slowly increase the temperature in the tank up to 81 to 83F (assuming you do not have sensitive fish or corals in the tank)
E)     Add a UV sterilizer if possible
F)     Carefully watch the remaining fish (if any) in your main tank for symptoms of the virus and remove them to a QT tank if they show symptoms
G)    Treat the infected fish(s) in a QT tank and follow one of the below treatment methods
H)    Do not add or change anything to the main tank for about 3 months after the last sign of the virus being in the main tank.  This includes keeping the previously infected fish in your QT tank.

The effectiveness of the above listed steps is a topic that is highly debatable as the only guaranteed way to get ich out of an infect tank, is to leave sit without any fish for a period of  about 3 months while maintaining higher temperatures in the tank.

Effective Treatments:
Based on my experiences and research, the below are the three best treatment options for treating a infected fish.  Please keep in mind that it is not recommend to try these treatments in your main / display tank.  Also, as the ich virus is actually in the skin of the fish, fresh water or medicated dips will most likely not be effective enough to properly treat the ich.  Treatment in a quarantine tank remains the most effective approach.  NEVER combine any two of these below methods (or any other methods) when dealing with ich.  Pick the best suited method for your situation and use only that one.

1. Copper Based Medications:  This is my preferred approach. I have had very good success with using a quarantine tank and treating with copper meds (like Coppermine by Seachem ) by following directions on the bottle.   After using the meds as directed, I will remove the meds from the set-up with a few large water changes and running carbon. If the ich is gone I will keep the fish in the QT tank for another  3 or 4 weeks just to make sure.  If it appears that the ich is not gone, I will treat again followed by a 3 to 4 week observation period as well.  The biggest drawback to this treatment is that some of the more sensitive fish may not be able to handle copper based meds (like mandarins).  Other treatments will have to be used for those fish.  Copper based meds can kill inverts and corals (even in trace amounts) so it is not suggested for use in your display tank. I would also suggest getting a copper test kit to ensure the level is maintained at 0.2 mg/l as higher levels start to become toxic to even hardy fish.

I have tried other non-copper based meds but found them not to be effective to break the ich life cycle and cure the fish of the infection.

2. Using Hyposalinity – This method involves using a QT tank with no meds, only lowing the salinity to 1.008 to 1.009 (11 to 12 ppt).  This needs to be done slowly never lowering the salinity by more than 0.004 within a 24 hour period. You will need a high quality / accurate refractometer for measuring your salinity.  Once the fish has lost all the ich spots, slowly rise the salinity to it normal level just as you have done to lower it. Keep the  fish in the QT tank for 3 or 4 more weeks to make sure. The biggest drawback of this method would be keeping your pH stable.  I have not personally tried this method, but a friend of mine swears by this approach having used it many times with very good success.

3. The Tank Transfer Method – This method involves using two different QT tanks and transferring the fish between the two tanks each day followed by completely cleaning the tank this fish was removed from before using it the next day.  This will break the ich life cycle.    I have no experience using this method.  The below link explains the process better than I can.


Preventing Ich from getting into your tank

It’s so simple, it actually seams too simple to work. You must first provide a set-up that replicates the fish’s natural environment (as best you can), and quarantine any new fish for 3 to 4 weeks before moving them into your main tank.  I will now always follow those two simple rules and have never had to deal with ich in my main tank ever since I have started following this approach.  I have, however, had to deal with ich in the QT tank after taking a new fish home allowing me to effectively treat and eliminate the virus before the fish is ever added to the main tank

Black Ich ????

You may have also heard of  black ich or black spot disease.   This is a disease that is most common in tangs and surgeonfish but not limited to them.  This is actually not a form of marine ich, but a type of flatworm and should be treated just as you would for other flat worms.  The symptoms can be every similar to ich with the obvious exception that the spots (when apparent) will be black and not white.




If you have any questions about anything in this article, feel free to go to our forum and post your question using the below link.  If you are not already a member, it will only take seconds to sign up.




6 thoughts on “Marine Ich (Cryptocaryon Irritants)”

  1. silver account

    There are many ways to treat marine ich and I will describe some but not all of them below. One possible treatment is to add copper to the water (0.15-0.25 mg/l or according to instructions). Copper is a very effective treatment but it should never be used in aquariums with lower life forms such as snails since it can kill them. Too much copper will kill your fish as well. Some fish species such as puffers are more sensitive towards copper than others. It is therefore important to research all the species in your aquarium before you use copper. Copper also has the disadvantage that it can’t be used in an aquarium with live rock and other calcareous media (coral sands etc) as they absorb the copper. Copper is one of the most commonly used treatments but not one of the best. Another treatment option for marine ich is to decrease the salinity of the water (1.009-1.010). A low salinity environment will kill the parasite and is harmless for most fish. You should keep the low salinity for 2-3 weeks. If you use this method it is important not to raise the salinity too quickly once the treatment is done. This method is not suitable if you keep invertebrates in your tank and some fish species will not tolerate it. The least intrusive way to treat this disease is by changing 50% of the water each day for two weeks. This removes the parasites. This method is most suited to be used for treating one fish in a hospital tank and not for an entire aquarium. It is very important to match the temperature and salinity of the old water when using this method. Malachite green can be used to treat this disease but is often less effective than above mentioned methods. Malachite green is supposedly reef safe (I haven’t tried it myself) but I still recommend treating in a hospital tank if possible.


    1. Cliff Post author

      Silver Account, those are all good points which are also discussed in the above article. One important thing to note, that if you are using water changes (or the tank transfer method), you should be doing this in a quarantine / hospital tank without any substrate in order to break the ich reproductive cycle. Thanks for posting a comment


  2. Derek

    I have a watchman goby in a quarantine tank. I lost the tank mates of the goby to ich. The goby has never shown any signs of ich and I have not medicated the tank. I was planning to leave the goby in quarantine for 5 weeks after the last fish died and then introduce into my main tank assuming it stays healthy. My question is should I medicate the goby prior to introducing to the main tank? Or will waiting 5 weeks be adequate. My concern is that even if the goby doesn’t show signs of ich it can still introduce it into my main tank.



    1. Cliff Post author

      I would suggest treating him for ich in your QT tank before re-introducing him to your tank. Better safe than sorry.

      If you lost all of the rest of the fish in your main tank, and it has no fish in it, I would suggest letting your tank sit empty for three months to ensure all the ich has died off in the main tank so you won’t re-infect your goby (or other new fish) when you put him back in the tank


  3. Alex Wilson

    To whom may concern, I would like to suggest an alternate version of the Transfer Method (Transfer Method II if I may) to eradicate Cryptocaryon irritans from new arrivals that I’ve had success with, in which sterilization and ammonia levels aren’t a concern nor is there a large amount of water wasted. In this method instead of two buckets or aquariums you simply use 5 permanent small quarantine aquariums where you transfer every 3 days. You then start over and reuse them without contamination concerns after 2 and half months or 72 days:

    – Day 1 – Start 5 small quarantine aquariums with a small amount of inert gravel using cycled water from an established Cryptocaryon free system and then wait a week to cycle or simply add freshly mixed water and wait a month to cycle. One air pump can be used with valves to run all five. Place your fish in the first quarantine aquarium.

    – Day 4 – After 72 hours transfer your fish from the first to the second quarantine aquarium with a net or other small container. This is easier to do at at night when the fish are asleep and sluggish.

    – Day 7 – Repeat transfer to the third quarantine aquarium.

    – Day 10 – Repeat transfer to the fourth quarantine aquarium.

    – Day 13 – Repeat transfer to the fifth quarantine aquarium.

    – Day 16 – Transfer to larger quarantine system (for further observation and treatment of other diseases) or optionally transfer directly to your main display aquarium.

    – Day 73 – After 72 days you can safely start over again with new fish using the same water.

    Please pass this information around and I hope it might help someone else.


  4. Pine

    Our fish started to get ich and we’re still not sure where the ich came from. The started off ass killing off one of my whole populations. That doesn’t seem that much surprising, so could that mean that our ich came from one population? After that population died off, my other populations started to show symptoms as well; the fish also started to show symptoms even before the whole ich infected population died off! I’m reusing tanks and pebbles and some decorations, but I’ve cleaned almost everything reused! Could there be ich still left in the gravel or reused filter that I’m using? Is it th grael or could it be the whole population that died off???


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