This is a common parasite which most aquarists eventually encounter. Even if you follow quarantine procedures you may at some point acquire an infected fish, which should be treated before being introduced into your main aquarium. The good news is that if handled correctly, this disease can be easily and permanently eliminated.
The scientific name for this nuisance is Ichthyophthirius
multifiliis, or “ich/ick” for
short. It is the largest known ciliated protozoan found on fishes. It appears
on the body and fins as tiny white dots resembling grains of salt; hence the
other nickname, “white spot disease.” These white spots may join
together to form white patches. Other signs of infestation can include excessive
flashing (rubbing against the substrate or decorations), labored breathing,
clamped fins, loss of appetite, lethargic and/or reclusive behavior, and hovering
near filter returns. Keep in mind, however, that all of these symptoms are common
with fish in distress and do not point directly to Ich. As a matter of fact,
flashing often occurs after routine water changes due simply to a fluctuation
in general hardness.
Ich has three life stages, which are important
to understand for proper diagnosis and treatment.
- When the parasite is visible to the naked eye, it is a nearly fully developed
trophont which has burrowed under the fish’s
mucus coating where it is protected from chemicals (medication). It has likely
been feeding on the body fluid of the fish for several days and has swelled
to many times its original size. At common aquarium temperatures of 75 to 80ºF
this feeding stage lasts only a few days, at which point the fully developed
cyst drops off the fish as a tomont.
- The tomont may swim for several hours
before settling on and attaching to the substrate, a plant, or some other surface.
During that time it is susceptible to chemicals and medication will be effective.
Once attached, it begins its reproductive stage. It encysts and begins rapidly
dividing. At this point, it is again immune to chemicals. Within a few days,
hundreds of new organisms burst from the cyst, sprout cilia and start swimming
in search of a host.
- These are now referred to as thermonts
or swarmers, and they must find a host within
a few days or they will die. (For this reason, we know that even an aquarium
heavily infested with Ich would be “clean” and safe for new fish
after only a week or two without fish in the tank.) Medication is effective
at this stage. Once the thermont attaches to a host and burrows in, it is referred
to as a trophont and the cycle begins again. Unfortunately, with each cycle
the number of organisms in the tank increases dramatically.
Left untreated, Ich is almost certainly fatal. Infected fish are weakened by
the ever growing number of parasites feeding on them. Secondary bacteria and
fungi attack more easily. Trophonts on the gills eventually restrict oxygen
flow and respiration is hindered. The ailing fish will ultimately succumb either
to the infestation itself or a secondary condition.
I came into the research phase of this article with certain misconceptions
about this parasite. It is a commonly held belief that the Ichthyophthirius
organism is always present in your aquarium
and needs only the right opportunity, such as stress resulting in a weakened
immune function, to attack your fish. Surprisingly, I found no scientific data
to support that claim. Credible sources state that there is no long-term dormant
stage this parasite can exist in. While its lifecycle is longer at low temperatures
(like that of an outdoor pond in a cooler climate), at average home aquarium
temperatures this parasite would likely complete a lifecycle in less than a
week. Considering that a single organism produces hundreds (if not thousands)
of offspring, the logical question is “where would they all go?”
Dr. Peter Burgess, writing for Practical Fishkeeping
magazine (who also co-authored the book entitled A to Z of Tropical
Fish Diseases and Health Problems), refers to the dormant concept
The proliferation of this myth could be due to the fact that it is possible
for a strong, healthy fish to resist severe infestations, especially if it was
infected previously and developed some resistance. While the organisms attach
easily to the gills of most fish (where they cannot be seen), the body may be
sufficiently protected by a tougher mucus coating. Such a fish could serve as
an asymptomatic carrier; potentially hosting many lifecycles without showing
any visible signs. When introduced to a new tank it brings the parasite with
it. Scaleless fish such as loaches and catfish often show symptoms first, but
most likely every fish in the tank will eventually be infected; if not visibly
on the body, on the gills at the very least.
It stands to reason that a stressed fish with a weakened immune function is
an easy host, but only if the parasite is present in the tank to begin with.
That brings us back to how to prevent it, now that we know it is not
lurking in every aquarium waiting to strike. Here are few guidelines:
- Never buy fish from a tank where any
fish show signs of disease.
- Quarantine new fish for 14-21 days and observe for any
signs of illness. Do not take “low dosage” preventative measures
against quarantined fish (such as half the recommended medication dosage) as
this would only spare the organisms most resistant
to medication. If you’re going to treat, do a full treatment just as you
would if you were certain the fish was infected.
- If you do not quarantine (not everyone has an extra tank set up), after
floating the bag and adding small amounts of your tank water to acclimate the
new fish, gently empty the bag into a net (working over a bucket) and then place
the netted fish in the aquarium. Never add the water from the
travel bag to your aquarium as it could contain Ich thermonts
or other dangerous organisms. Still, your fish could have trophonts on the gills
or on the body which have not swelled enough yet to be visible. You’re
gambling with the health of all your fish if you don’t quarantine.
- If you keep multiple tanks, use separate nets for each
tank and/or let your net dry completely
between uses. Ich cannot survive being dried out.
- Buy plants only from tanks without fish,
or quarantine plants for 5-7 days without fish, or
bathe plants in potassium permanganate before putting them in the main tank
(unfortunately this can be hard on the plants).
- If your tank does become infected, be accurate and thorough
with treatment to ensure total eradication. It only takes
a single surviving trophont to reproduce and start the whole ugly process again.
There are many over-the-counter medications for ich. They all boil down to
a few common ingredients, each of which has a downside. In addition, Ich outbreaks
often accompany cycling problems and it is difficult to keep up with frequent
small water changes (to minimize ammonia and nitrite levels) while dosing with
a medication that advises not to do any
water changes during treatment. With that said, I’ll start by recommending
my first two choices for treatment, which are more “natural” (or
at least less “chemical”) and should be easier on your fish, your
biological filter, and your wallet.
There are two schools of thought regarding raising the temperature of the water
to treat ich.
- The first approach is used simply to speed up the lifecycle
of the parasite, since whatever medication you choose will only be effective
on the free-swimming tomonts and thermonts. It is understood that at temps above
75ºF, for example, an entire lifecycle can be complete in less than 4 days.
(In contrast, it can take more than 5 weeks at temps below 45ºF, such as
you might find in an outdoor pond.) Slowly raising the temperature a few degrees
above normal (to approximately 80 - 82ºF) will do the trick, and you can
treat accordingly with salt or a medication (see below). Always maintain good
surface agitation, especially with a higher temperature.
- The second approach is to actually destroy the organism with heat, and can be combined with the salt treatment below, but not with meds. The data I studied (including a report by the Southern Regional Aquaculture Center, which is currently archived here) suggests that most strains of Ich cannot reproduce at temperatures above 85ºF. To use this treatment approach, slowly (no more than 1 or 2 degrees per hour) raise the temperature to 86ºF, while maintaining strong continuous surface agitation to oxygenate the water. This is extremely important because water holds less O2 at higher temperatures. (This is why meds should not be used in conjunction with high temp – most Ich treatment products also reduce oxygen levels. Less available oxygen, combined with the respiration difficulties an infected fish is already faced with, could be fatal.) You can angle powerheads up toward the surface, or lower your water level to get a little extra splash from your filter return. As with any treatment, observe your fish closely for signs of stress (labored breathing, erratic behavior) and reduce the temperature slowly if necessary. (A note to the wary; my Malawi haps and clown loaches endured a temperature of 88ºF for 10 days with apparent ease – I never detected the slightest hint of distress – and the Ich was completely wiped out. One article that I read suggests the temperature be raised to 90ºF!)
The adjusted temperature should be maintained for approximately 10 days, or
a minimum of 3 days after all signs of the
parasite have disappeared. Do not discontinue treatment when
the spots go away. This is critical, because we know that
they are visible only as a trophont on the body of the host, and not during
the reproductive or free-swimming stage. We also know that trophonts on the
gills are impossible to see.
One last note on raised temperature treatment:
If you follow the directions here thoroughly and have a subsequent outbreak
without having added new fish or plants, you may need to try a different approach.
It is possible to encounter a resistant strain of ichthyophthirius, as there
have been rare instances recorded where the organism survived at 92ºF!
Salt is frequently recommended for treating a myriad of fish diseases, especially
those involving external protozoa and fungi.
What kind of salt? We are not talking about
“marine salt” or “cichlid salt” (both of which typically
contain a blend of mineral salts and trace elements specially formulated for
aquarium use to simulate ocean or rift lake water chemistry). You want sodium
chloride (NaCl). “Aquarium salt” is the most widely used form because
it does not contain the iodine or anti-caking agents that table salt does. I
will say, however, that several credible sources assert that the minute amount
of additives in table salt are harmless. Robert T. Ricketts, writing for AquaSource
online magazine, puts it best with “any water-living vertebrate would
be pickled in brine well before toxic concentrations of iodine could be reached.”
Still, others offer strong warnings about the dangers of iodine and prussiate
of soda (an anti-caking agent) and suggest “canning salt” as a cheaper
alternative to aquarium salt. Make your own choice, but since I’ve heard
only warnings and no actual accounts of fish death by table salt, I assume it’s
most likely the ‘better safe than sorry’ principle at work here.
“Sea salt” is another option, and is generally available in nutrition
stores because it is considered a more “natural” form of salt. It
does not contain iodine, but may have anti-caking agents. I have used it in
my aquariums without incident.
Can my fish handle salt? I wrote this article
with African rift lake cichlids in mind, and I have successfully exposed my
Malawi haps and clown loaches to a salt treatment without any problems. But
these fish are accustomed to fairly hard water with a high pH. It is my understanding
that species preferring soft water will not tolerate salt as well. If you keep
soft water fish, please do your homework before proceeding with salt.
How much? I visited websites and read articles
on treating Ich in generic freshwater fish, food fish, guppies, loaches, and
African rift lake cichlids to name a few. I encountered dosage recommendations
ranging from about 1.75 tablespoons to 6 tablespoons salt per 5 gallons of water.
One rift lake cichlid importer/breeder uses “1 handful” of salt
per 5 gallons of water. I concluded that my fish can probably tolerate more
salt than I think, at least on a short-term basis. Based on everything that
I’ve read to date, I would feel comfortable adding 2-3 tablespoons salt
per 5 gallons if I were also using the high temperature treatment outlined above.
If I were using salt alone, I would work my way up to 4-5 tablespoons per 5
gallons. We don’t want to skimp on our treatment if we hope to permanently
eliminate this pest. Salt should be added slowly over the course of
24-48 hours or so (always dissolve in a small container of tank water first).
Keep a close eye on your fish and perform an immediate water change if they
show any additional signs of stress (beyond what the Ich is already causing).
How long? The salt bath should be maintained
for approximately 10 days, or for at least 3 days after
any visible signs of Ich can be detected. Do not discontinue
treatment when the spots go away. If you use a higher dosage
of salt, watch the duration more closely. One article (on guppies) specifically
stated not to leave the fish in salt longer than ten days, but their dosage
recommendation was on the high end at 5 tablespoons per 5 gallons.
What else should I do? The salt bath can
be used on its own, or in conjunction with a temperature adjustment as described
in the section above. A water change can be performed during the salt treatment
(but is not necessary unless nitrates are creeping up to an undesirable level).
Be sure to salt the replacement water accordingly to maintain salinity. Gravel
vacuuming is also helpful to remove as many tomonts as possible before they
can release offspring. Again, this is not absolutely necessary since the salt
should destroy the free-swimming thermonts upon their release.
At the end of the treatment, do several large (40-50%) water changes with dechlorinated
unsalted water to reduce the salinity to normal.
One last note on salt treatments: If you
follow the directions here thoroughly and have a subsequent outbreak without
having added new fish or plants, you may need to try a different approach. It
is possible to encounter a resistant strain of ichthyophthirius, as there have
been rare instances recorded where the organism survived in water salted at
more than 5 tablespoons per 5 gallons.
As stated previously, there are many products available
for treating ich. Whatever you choose, be sure to:
- Read the label thoroughly for
dosage information, special instructions, and warnings related to your own health
and that of your plants, invertebrates, and scaleless or sensitive species of
- Perform a water change and vacuum
the gravel before medicating. Most meds are less effective with excessive dissolved
organics (nitrates) present and you’re often instructed not to change
any water during treatment.
- Remove the carbon from your filter.
- Maintain good surface agitation and water movement.
This is always important, but it is absolutely critical when raising
your water temperature and administering meds – both of which reduce the
oxygen content of the water and can kill your fish if care is not taken. For that reason, it is not advisable to raise the temperature more than 2 degrees above normal when using any of the following Ich treatment products.
- Continue treatment for the duration advised.
Because of the lifecycle of the parasite it is critical that you
continue treatment for a minimum of 3 days after any visible signs of Ich can
be detected. Do not discontinue treatment when the spots go away. If the instructions
advise you to retreat, do so.
- Disregard grandiose claims. Some
products claim to “cure ick within 24 hours.” Based on what we know
about the lifecycle of this parasite, that is simply not possible.
Copper-based medications are commonly recommended
for treating ich. Some brand names include CopperSafe® by Mardel,
General Cure® by Aquarium Pharmaceuticals, and Aquari-Sol®.
Look for the active ingredient “copper sulfate” or “soluble
copper salts.” Copper does not stain and is highly recommended by some
aquarists. It does have drawbacks, however. It causes oxygen concentration to
drop, it is toxic to snails and invertebrates, it may not be tolerated well
by scaleless fish and plants, and like any chemical, it can certainly be toxic
to your fish especially if dosed incorrectly. Apparently the toxicity increases
as total alkalinity (KH) decreases. This would suggest that copper-based meds
may be better suited for use with African rift lake cichlids than with soft
water fish from low pH/KH conditions. But beware; if you should have a drop
in your pH while using copper your fish could perish.
Potassium Permanganate has been suggested
as an alternative to copper for treating ich, especially in soft water fish.
It is primarily used in ponds, and is not in my opinion the best choice for
aquarium use. It most certainly is not for the beginner. It can be purchased
under its chemical name, or found as the active ingredient in products such
as Flukes Control® by Aquatronics. As with so many chemicals, there’s
a fine line between calling it a wonder drug and a lethal substance. It is not
really a medication but an oxidizing agent that reacts with organic material,
resulting in the destruction of external bacteria, fungus and parasites. For
that reason, it is considerably less effective with excessive nitrates present,
because its oxidizing power is “used up” on the dissolved organics
in the water and is consequently not effective against the target pathogen.
It is often used by retailers as a dip for incoming plants, to eliminate snails
and their eggs. It is toxic in high doses, especially in high pH water; there
are better choices for treating African rift lake cichlids. It is not safe for
eggs and fry, and excessive treatments can cause gill damage in adults. It will
damage your biological filter, kill algae, and reduce oxygen concentration in
the water; strong aeration and water movement is critical. It can be tough on
live plants and catfish, and should not be combined with any other chemicals
– especially Formalin. It can burn your skin and eyes, and will stain
your hands and clothing brown; gloves are recommended. It cannot be removed
with carbon like other meds; it is neutralized with hydrogen peroxide but I
don’t know exactly how that is accomplished safely in the aquarium. Again…
this is for the advanced fishkeeper.
Formalin is a form of formaldehyde and
is often used by fish farmers and home aquarists to treat ich. It can be purchased
under its chemical name, or found as the active ingredient in products such
as Ick Guard II® by Jungle, and Formalite III® by
Aquatronics (which also contains copper). While it is non-staining and said
to be safe for live plants (and at lower dosages…) scaleless fish, eggs
and fry, it is nevertheless a strong chemical – a preservative for biological
specimens (AKA embalming fluid). It may damage your biological filter, deplete
oxygen levels in the aquarium, and destroy invertebrates and weak fish. Its
toxicity increases with water temperature and acidity, making it a questionable
choice for soft water fish.
Malachite Green is an ominous substance
that’s highly effective against Ich and fungi. It can be purchased separately
under its chemical name, or found as the active ingredient in products such
as Maracide® by Mardel, Ich Cure® by Aquatrol, Super
Ich Plus® by Aquatronics, and Fungus Plus® by Aquatronics.
It is carcinogenic and dangerous to handle or breathe (especially for pregnant
women). There are rumors circulating that it could be banned for aquarium use
by the FDA in the future. It cannot be used on food fish and is toxic to eggs,
fry, some varieties of tetras, catfish, elephant noses, loaches and small marine
fish. It also may damage your biological filter and will likely stain aquarium
decorations and silicone sealant. Malachite Green is light sensitive, and you
will be advised to keep your aquarium lights off during treatment to prevent
the chemical from oxidizing.
Formalin and Malachite Green are often
used in conjunction with one another. The two chemicals are said to have a synergistic
effect when combined, having a greater impact together than either one by itself.
Products include Rid-Ich+® by Kordon,
Quick Cure® by Aquarium Products,
Cure-Ick® by Aquarium Products,
Ick Guard® by Jungle,
and Formalite I® by Aquatronics.
This combination of chemicals is probably the most common choice for
Acriflavine is a chemical found in some
Ich medications such as Ick Clear® by
Jungle, and Acriflavin Plus®
by Aquatronics. It is considered to be highly effective against
protozoan parasites, as well as external bacterial infections and fungus which
sometimes occur as a secondary condition. It may damage your biological filter,
harm live plants, cause skin irritation, and stain your hands and tank decorations;
gloves are recommended. I do not know how well it is tolerated by invertebrates,
sensitive species, scaleless fish and fry, but I do know that it cannot be used
on food fish – which is sometimes a clue as to the toxicity of the substance.
As always, read warning labels thoroughly.
Methylene Blue is used primarily for superficial
fungal or bacterial infections, and nitrite or cyanide poisoning. It is also
considered to be an alternative to Malachite Green for the treatment of fungus
and external protozoa in sensitive fish, eggs and fry. It is available under
its chemical name or in products such as Methyblu®
by Aquatronics. It too cannot be used on food fish, and is
a powerful dye that may stain tank decorations and silicone sealant. Damage
to plants and biological filter may also occur.
There are other antiparasitic medications
available, but I believe I’ve covered those most commonly used. Clout®
by Aquarium Products is one more worth mentioning since it
appears on nearly every LFS and pet store shelf that carries fish and is often
recommended as a cure-all. It is an extremely strong blend of medications which
I am unfamiliar with, including dimethylamino, phenylbenzylidene and cyclohexadien.
I believe it is best suited for internal parasites. It is definitely not to
be used with scaleless fish. Read the label carefully.
There are a few products that have been developed which take a completely different
approach to treating Ich than those outlined above. One is Stop
Parasites® by Chem-Marin. It utilizes
a proprietary blend of food-based ingredients including hot peppers, which may be safer for you and your fish than traditional meds. According
to its creator, the product took eight years to develop. It apparently stimulates
the fish’s slime coat production to excess, which causes the parasites
to slough off, or be shed. Then it provides a “false host” for the
parasites to feed upon which is more desirable than the fish. Kent Marine makes
a similar product for saltwater parasites called RxP®.
I cannot endorse either product, never having used them, but if you are open
to homeopathic-type treatments and want to experiment with something other than
salt or raised temperature, this product might be for you.
Most strains of Ich will respond to the treatments described here. However,
researchers have recorded rare instances where trophonts were able to encyst
and reproduce without leaving the body of the host fish, essentially skipping
the second life stage described above. Obviously this is a menacing thought,
but one to be considered should all attempts to eradicate the parasite fail.
In such an event, it would be impossible to destroy all the organisms and the
frustrated hobbyist would fight an endless battle with repeated outbreaks of
the disease. Euthanasia would be the only humane option. Let me stress, however,
that I read about this in a research paper and have never heard of this actually
occurring to a fellow aquarist. Let’s hope it never does. □