Marine Ich

Marine Ich (Cryptocaryon irritans)  

What You Need To Know:

* Mild fish parasite which is often managed by using a UV Sterilizer, Ozone, Diatom Filter, Oxydator, herbal remedies, enhanced nutrition, etc. etc.
* Can be treated in a quarantine tank using Hyposalinity, Chloroquine, Copper or Tank Transfer Method.
* The fallow (fishless) period for starving ich out of a Display Tank is 76 days. Or new data suggests that raising aquarium temperature to 27C/80.6F can shorten the Ich fallow period to just 6 weeks!
* Primary symptom is salt or sugar-like “sprinkles” on the body & fins (see photos below):

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Understanding Marine Ich

Unlike most other diseases, Marine Ich (Cryptocaryon irritans) has been well studied and documented due to its prevalence and threat to the aquaculture industry. The life cycle of this parasite is well understood, and treatment options have been thoroughly tested. The purpose of this article is to give the hobbyist a basic understanding of ich, its life cycle and treatment options. Lastly, observations, claims and common myths will also be discussed.

Terminology – The following terms are used to describe the various stages of ich’s life cycle:

Trophont: The “feeding stage” of the parasite that attaches itself to the fish, commonly associated with salt or sugar-like “sprinkles” on the body or fins. These sprinkles are not the actual parasite, as all stages of ich are invisible to the naked eye. Each white dot is actually caused by excess mucous which forms around the area where a trophont latches onto the fish. This is the fish’s immune response to the parasite. With ich, the trophont burrows in under the epithelium (outer skin layer), is oval shaped, and ranges in size from 48 x 27 to 452 x 360 micrometers. A fish carrying trophonts doesn’t always have visible symptoms, as the gills are easier to penetrate, and those trophonts will be out of sight. Trophonts in the gills cause excess fluid to build up, making it more difficult for the fish to breathe.

Protomont: The stage where the parasite drops off the fish, before becoming a tomont. Protomonts crawl around looking for surfaces to encyst upon.

Tomont: The “encysted stage” which adheres to rocks, shells, substrate – and even possibly corals/inverts. Tomonts produce “daughter” tomites, which are then released into the water column as theronts.

Theront: The “free swimming” stage which seeks out fish to infect/feed upon. Theronts are the only stage eradicated by chemical treatments (e.g. copper) and hyposalinity. It is also possible to cross contaminate with theronts by sharing water between tanks or via aerosol transmission. Once a theront finds a fish host and attaches, it becomes a trophont and the life cycle begins anew. (This can continue almost indefinitely until the theront life stage gets interrupted by copper, hyposalinity, etc.)

Life Cycle – Marine Ich is most often introduced into an aquarium by a fish infected with trophonts. However, cross contamination via theronts or from tomonts brought in on a coral/invert are other possibilities. Assuming we are dealing with a fish carrying trophonts, this is how the life cycle plays out:

Credit: Charles Raabe

1. A trophont will typically spend 3-7 days feeding on a fish, before dropping off to become a protomont.

2. The protomont crawls around for 2-18 hours, looking for a surface to encyst upon. Once it finds this, it sticks to the surface, and begins the encysting process. The parasite is now called a tomont.

3. It takes about 8-12 hours for the cyst to harden around the tomont. After this, the tomont goes into “reproductive mode” producing numerous daughter tomites. These tomites are then released into the water column as theronts. How long it takes for theronts to be released varies greatly, depending upon water temperature, which strain of ich you are dealing with, etc. The average time is 2 weeks, with 35 days usually being the maximum (see table below). However in at least one study (Colorni and Burgess 1997), it took 72 days for all the theronts to be released from a group of tomonts.

4. The now “free swimming” theronts seek out fish to feed on, thereby becoming trophonts, and the cycle starts all over again. A given strain will die out after 100 generations or so. Given the average life cycle of ich is 2 weeks, this could take almost 4 years (on average).

As you may have noticed, the timing for each stage to “move forward” to the next varies considerably. Therefore, ich is rarely in sync. For example, it is not unusual for a fish to be battling trophonts, while simultaneously theronts are swimming around looking for a host to feed on. This is especially true if your tank is plagued by more than one strain of ich. It’s this “perfect storm” that sometimes allows ich to overwhelm an immune system and the fish dies.

Treating Marine Ich

Marine Ich (Cryptocaryon irritans) is best described as salt or sugar-like “sprinkles” on the body or fins. Sometimes however, the parasite can harbor inside the gills – out of sight. Behavioral symptoms such as flashing, scratching, twitching and heavy breathing are other indicators of ich.

Most hobbyists will encounter ich at some point in one of two settings:

1) A newly acquired fish in a quarantine tank (QT) – proceed to “Treatment options” below.

2) Fish in the display tank (DT) – There is no easy way of dealing with this. Even in fish only systems, it can be problematic trying to treat in the DT. Copper (and other medications) can be absorbed by rock/substrate, and doing hyposalinity risks possibly wiping out your bio-filter. You have to catch ALL of your fish, and quarantine/treat using one of the treatment options mentioned below. The DT itself should be left fallow (fishless) for 76 days to starve out any remaining parasites. Continue to periodically feed your corals/inverts; a pinch of flake food every 2-3 days will help maintain bacteria levels in the DT. Remember there is no “reef safe” ich treatment that will actually eradicate all of the parasites! Tea tree oil from India or garlic extract or any other herbal/natural “medication” is designed to only help fish manage their symptoms.

Treatment options:  Copper, Chloroquine phosphate, tank transfer method, or hyposalinity. Best administered in a quarantine environment. All treatments are listed here with links to more info:

Observations, claims and common myths

Ich is unavoidable; it exists in every tank. FALSE. Ich doesn’t just appear out of nowhere. It is a ciliate protozoa that is either brought in on an infected fish or from water, rock, coral, etc. that was taken from an ich-infested environment.

You can see ich on a fish. SOMETIMES. Seeing white salt or sugar-like “sprinkles” means the parasite has successfully penetrated the fish’s mucous coat. However, harboring in the gills offers the path of least resistance, and oftentimes that is where the parasite is most frequently found (out of sight).

All spots are ich. FALSE. Ich is often misdiagnosed. A white spot on a fish can be Lymphocystis (a harmless virus), or something more serious like Brooklynella, Uronema or the beginnings of a bacterial infection. If a fish is completely covered in sprinkles, then this could mean Marine Velvet Disease (Amyloodinium) – a potential tank killer.

Certain fish (e.g. tangs) are ‘ich magnets’. TRUE. Tangs (especially Acanthurus) have a thin mucous coating protecting their skin, making them more vulnerable to parasites. Conversely, fish such as wrasses, clownfish and dragonets have a thick mucous layer which affords them greater protection.

Cleaner wrasses/shrimp eat ich. FALSE. Ich trophonts get under the epithelium (outer skin layer), which is out of reach for them. What you are seeing them pick at is dead skin tissue. It is possible for cleaner shrimp to eat velvet, flukes, Lymphocystis – any pathogen which remains on the surface of the skin.

Ich goes away on its own.MOSTLY FALSE. So long as fish are present, ich continues its life cycle for almost 4 years (on average). If another fish is introduced with ich, the new strain restarts the 4 year clock. The only way to eradicate ich from your tank is to go fallow for 76 days, treat all your fish and quarantine all livestock moving forward!

There are ‘reef safe’ medications that kill ich. FALSE. While these remedies may help fish deal with their symptoms, none can eradicate the parasite from your aquarium. The day someone does finally develop an effective “reef safe” treatment, we are all going to hear about it, and the inventor will become a millionaire.

You can beat ich by running a UV, feeding heavy, garlic, etc. SOMETIMES. People who practice “ich management” have mixed results. Typically, experienced hobbyists fare better than newbies. However, random “mysterious” fish deaths and not-so-healthy looking fish is often the price of “ich management”.

Certain fish are immune to ich. SOMEWHAT TRUE. There is both disease resistance and immunity to consider. The longer a fish is exposed to a particular pathogen, the more familiar the immune system becomes with it and how to fight it. This is a calculated risk however, as one can only hope the immune system “muscles up” before the parasite/worm outright kills the fish. It is thought that these fish develop histone-like proteins in their mucus and skin that kill trophonts. However, these fish are still carriers (so they can infect other fish), but they themselves may not show symptoms for up to 6 months or possibly longer. There is also “disease masking”: Any fish coming from a tank dosed with a non-therapeutic level of copper may not show symptoms of ich for up to 1 month after being removed from it.

Ich can survive almost indefinitely without seeing any body spots or just a spot or two, because it often resides in the gills. TRUE.

All fish have ich. FALSE. In the wild, the infection rate is about 30%. However, most wild fish can survive minor outbreaks since there’s about a gazillion gallons of water diluting those parasites from the fish. In our relatively small aquariums, fish are often overwhelmed by a much higher concentration of parasites.

Once a fish has ich, he will always have it. FALSE. A fish can be “cleansed” of ich (or any other disease) by using a suitable treatment in a quarantine environment.

If ich can’t always be detected, why bother to quarantine? In the confines of a small quarantine tank, symptoms of ich will almost always manifest themselves. Even if you don’t see white dots, behavioral symptoms such as scratching, flashing, head twitching and heavy breathing should be present. Prophylactic treatment is a wise course of action even if ich is just suspected.

More info regarding Marine Ich can be found in the links below: