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Ich (Ichthyophthiriasis multifiliis)

Ich (Ichthyophthiriasis multifiliis)

Ich (Ichthyophthiriasis multifiliis)

Ich (Ichthyophthiriasis multifiliis)

Ich (Ichthyophthiriasis multifiliis) known to tropical fish keeping enthusiasts as White Spot Disease, is a parasitic ciliate that is arguably the most common ailment of all brackish, freshwater, and marine aquarium species.

Ichthyophthiriasis multifiliis is a protozoa that is wide spread in all freshwater fish but appears to be more common in aquarium species that are kept in close contact.

Almost every tropical fish keeping enthusiast at one time or another has housed fish that developed Ich, which is responsible for more fish deaths than just about any other fish disease.


The life cycle of the Ich parasite includes a trophozoite (feeding or encysted) stage, a mature trophont stage, and an infectious theront (tomite) stage.

During the encysted stage, the Ich protozoan is called a trophozoite. The trophozoite attaches itself to the fish and begins to feed on the skin and tissue. As the protozoan continues to move around in the cyst feeding and growing on the tissue, the fish’s body will try to further encapsulate and wall it, off causing tremendous irritation.

Ich (Ichthyophthiriasis multifiliis)

Ich (Ichthyophthiriasis multifiliis)

The trophozoite eventually matures and is then referred to as a “trophont.” Each mature trophozoite (trophont) that falls off the fish will burst through the cyst wall and fall to the bottom of the aquarium where they begin to divide into thousands of new Ich infecting units called theronts (tomites).

The theronts, or tomites, are motile and swim around the tank looking for a fish to attach themselves to.

It is important to note that Tomites will only survive for 48 hours, however, if they can’t find a fish to attach to they will attach themselves to plants, rocks, filter media, etc. If you move a plant, piece of driftwood, or decoration from a tank infected with Ich, you have just infected the new tank.

Unless killed, the tomites will eventually penetrate the skin and gills of a new host to repeat the life cycle.  Depending on water temperature, the entire life cycle can take anywhere from 4 days to several weeks.

The encapsulation by the body of the fish during the trophozoite stage is why the Ich parasite is so difficult to treat in an aquarium environment.   Most medications cannot penetrate the wall of the cyst during this stage to destroy the Ich parasite.

The life cycle of the Ich parasite during the tomite stage progresses faster at higher water temperatures.   At 78-80 F, replication is completed in about 8 hours.   When replication is completed and the newly formed tomites are released into the water column, the parasite is most susceptible to a successful treatment regimen.

At lower temperatures replication takes considerably longer, as does treatment.


Ich (Ichthyophthiriasis multifiliis)

Ich (Ichthyophthiriasis multifiliis)

Fish infected with Ich will be covered with white spots on the body and/or the gills which causes severe irritation.  Infected fish will try to rub or scratch off the protozoa on the sides and bottom of the aquarium.

As the disease progresses, the fish will display severe agitation, loss of appetite, respiratory distress, and eventually death.


Some or all of the following behaviors are symptoms of Ich infected fish:

  • Abnormal behavior such as isolation, inactivity, etc.
  • Anorexia or loss of appetite
  • Balance problems
  • Discoloration
  • Flashing, rubbing, or scratching against objects
  • Increased breathing rate (hyperventilation)
  • Resting on the bottom
  • Swimming upside down near the surface

Microscopic identification of an Ich lesion scrape will show a cyst between .5 and 1.5 mm in diameter with a horseshoe shaped nucleus.


The primary cause of Ichthyophthiriasis is stress, with the most severe stress occurring during the shipping and handling of new fish.

Most fish that come in contact with the protozoan have strong immune systems that fight off the disease, but when the immune system is diminished and not functioning properly, usually because of stress, the lowered immune response allows the disease to take hold in the fish.

Farm raised and wild specimens imported by wholesalers, who distribute them to retailers, who finally sell them to tropical fish keeping enthusiasts, endure a tremendous amount of stress.

The Ich parasite is so wide spread that it is already present in a good number of collector’s, breeder’s, and wholesaler’s breeding ponds, holding tanks, and large aquariums.

Water quality, rapid changes in water temperature, improper diet, improper acclimation, shipping and handling, bullying by tank inhabitants, and a variety of other factors in an enclosed environment are all causes of stress that lowers the immune response in fish.

This is why Ich is most prevalent in newly purchased specimens.


We seldom recommend treating an entire tank for a disease, but Ichthyophthiriasis is the exception.

Because you cannot kill Ich while it is on the fish, removing the infected fish from a community tank to a quarantine tank does not solve the problem.

All effective Ich treatments are designed to kill the tomite form of Ichthyophthiriasis while it is in the tank.  The mature Ich organism (white spots) that you see on the fish does not die from the treatment, but will drop off in a couple of days during it’s normal life cycle.

The life cycle of the tomite is temperature dependent and because Ich can only be killed in the tomite stage, raising the tank temperature to between 78 and 80 F for at least 48 hours will speed up the life cycle and the parasites release from the host.

At higher temperatures, it takes approximately four days for the Ich life cycle to be completed.  However, at lower water temperatures (around 60 F) that goldfish and Koi prefer, it could take up to several weeks for any treatment to be effective.

When one fish in an aquarium has Ich, assume that the entire tank is contaminated.

You can treat the tank several ways.


Most tropical fish are able to withstand temperatures around 86 degrees or more for short periods of time, but make sure your species can cope with higher temperatures before using this treatment.

Gradually raise the temperature in the tank to 90 degrees F. and hold for a period of two weeks.   To avoid stressing the fish, do not raise the temperature more than 2 degrees F every twelve hours.   After two weeks, bring the temperature back down to normal conditions.

The Ich in the tank will die in about 2 days, but keeping the temperature for two weeks will ensure an Ich free tank.

Keeping the water temperature (without fish) at 96 degrees F. for 3 to 4 days will completely eradicate Ich from the tank.


Sodium chloride (NaCl) is effective against fungus, bacteria, external parasites, and provides essential electrolytes to fish.  Because it is cheap, readily available, never expires, and is easily used in low to high concentrations; it has been used by tropical fish keeping enthusiasts for years as an all around medication, but it has it’s drawbacks.

It cannot be used with most live plants, inverts, and scaleless species, and it is often difficult to determine the correct dosage for each species.  Salt overdoses have wiped out many freshwater aquariums.

Despite it’s drawbacks, here are three useful treatments.

1 Tbsp Salt per 3 gallons of water

Adding 1 tablespoon (Tbsp) of salt per 3 gallons of water will slightly irritate the slime coat on most species that creates a beneficial mucus on the skin that blocks parasites and microorganisms from harming the fish’s body.   Except for anchor catfish, this treatment is safe for most species.    Keep infected fish at this concentration for a week or so and increase if there is no improvement.

1 Tbsp Salt per 2 gallons of water

A concentration of 1 Tbsp of salt per 2 gallons of water combats a wider range of illnesses like Ich.   Keep infected fish in this concentration for 10 days or more and increase the dose if possible, if there is no improvement.

1 Tbsp Salt per 1 gallon of water

A high concentration of 1 Tbsp of salt per gallon of water will knock out virtually every illness however, it can be detrimental to scaleless fish and several other sensitive species.

Rasboras, danios, tetras, silver dollars, livebearers, most cichlids (and their fry), and even Neocaridina cherry shrimp are relatively salt tolerant.

Because salt does not evaporate or get filtered out of the water, overdoses most often occur when performing water changes.   Only add salt in proportionate amounts when doing water changes to maintain the necessary treatment level.

For example, if you are treating 100 gallons of water for Ich with 1 tbsp salt for 2 gal. water, you will initially need 50 Tbsp of salt.   If you make a 20% water change (remove 20 gallons of water), you need to add back 20% of the salt (or 10 Tbsp) to the new water to maintain the same concentration.

Unlike most medications, salt does not break down over time.

Salt and Heat:

Motile tomonts and theronts cannot survive in water with more than a trace of salt.   By increasing water temperatures and raising the salinity of the aquarium, the Ich parasite can be eliminated without harming more delicate species like such as elephantnoses and loaches.

Raise the water temperature to 82 – 86 degrees F. and gradually increase the salinity in the aquarium to 2 tsp/gal.   Instead of adding the salt directly into the tank; make a brine solution at the recommended ratio and over a few hours add it to the tank.

For example: When treating a 10 gal. aquarium, dissolve 20 tsp. of salt into a jug of warm, dechlorinated water and gradually add to the tank over a few hours.

Keep the salt in the tank for two weeks and gradually lower the salinity and temperature back to normal.

OTC Medications:

Over the counter Ich medications can be used to treat freshwater aquariums with species like tetras, barbs, cichlids, gouramis, livebearers, and goldfish but loaches, catfish, morymyrids, pufferfish, eels, and inverts like shrimp and snails react badly to many of them.

Malachite Green and formalin are good medications when used separately or in combination, and are readily available.   Methylene blue and copper treatments are also commonly used.

When using formalin products, it’s important that the product is fresh.   Old or outdated formalin precipitates into paraformaldehyde which is poisonous to fish.

Malachite green given at the recommended dose can also be toxic to some species like neons, piranhas, inverts, and many scaleless fish. Treat these fish with half the recommended dose and remove inverts.

Baths of salt, potassium permanganate, and quinine hydrochloride are also used but show no advantage over the more readily available medications.


Fresh garlic cloves, garlic juice, and/or commercial garlic products have been successfully used to eradicate Ich in tanks where snails, plants, shrimp, and delicate fish species are housed.   OTC products like Kent Garlic extreme or Sea Chem Garlic Guard mixed with the fish’s food improve the fish’s appetite and eliminate Ich sometimes within a couple of days.

Home made concoctions of freshly shredded and squeezed garlic cloves mixed with a bit of RO or tank water left overnight in the refrigerator and soaked into wafers, pellets, or sticks are proven cures.

In addition, a clove of garlic sliced, halved, or cut into quarters placed into the tank seems to eliminate the parasite in just a few days.  The garlic leaches into the tank water and the fish also seem to relish it.   For saltwater fish and freshwater species like plecos, catfish, snails, etc., where other products cannot be effectively used, it should be looked into.

Many tropical fish keeping enthusiasts remove all the fish from the community tank and raise the temperature to about 86 degrees F. or more for a couple of weeks before placing the fish back into the tank.

The removed fish are treated under observation in a medicated isolation tank to clear up the infection before being returned to the original tank.


  • Only buy fish healthy fish that are free of all signs of disease.
  • Never buy fish from a tank that contains dead, dying, or diseased fish.
  • Do Not buy plants that are kept in a tank with sick or diseased fish.
  • Quarantine all purchased fish and plants for a minimum of two weeks before introducing them into a community tank.
  • Avoid buying newly acquired fish from retailers. Wait a week or so before purchasing them.
  • Buy fish from the source when possible to reduce the amount of stress from shipping and handling.
  • Avoid temperature, pH, Nitrate, Nitrite, and ammonia fluctuations to reduce stress.
  • Avoid overstocking your tanks.
  • Immediately remove any fish that show signs of Ich into a quarantine tank.
  • Maintain pristine water quality with regular water changes.

Following these guidelines and treating infected fish promptly will greatly reduce the incidence of Ich (Ichthyophthiriasis multifiliis) and many other deadly diseases.

Posted in Featured Articles, PARASITIC INFECTIONS, Tropical Fish Diseases, Tropical Fish KeepingComments (4)

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