MYTHBUSTER: ALL the well-done scientific studies by researchers on heat and ich have found heat to be totally ineffective in treating ich!
Note there are two other diseases that look like ich (tetrahymena in livebearers and epistylis in other fish). So make sure you have ich.
Public Aquariums use formalin/malachite green (Ich-X, Rid-Ich Plus, Blue Planet White Spot Remedy, and Mardel QuickCure) to treat ich in freshwater fish, as do University Research Centers, Cory of Aquarium Co-op, and Joey.
- NEVER turn off the filter, remove the filter, change the filter media or clean the filter media. If the carbon has been in the aquarium for more than two weeks do NOT remove it (contrary to some directions). This is VERY important.
- Do NOT move the fish to a quarantine tank (contrary to some directions).
- Formalin and malachite green are both toxic in large enough dosages so carefully follow the dosage directions on the medication bottle.
- If one raises the temperature with formalin/malachite green the medication can become somewhat toxic.
- Cory and others have treated thousands of “scaleless” fish with full strength formalin medication with absolutely no problem.
- Formalin/malachite green is not poisonous to snails or shrimp at the proper dosage.
- At 76 degrees formalin and malachite green need to be added every day to be effective.
- Follow the directions on the medication as to water changes.
The seminal study on ich treatments (Tieman and Goodwin, 2001) found salt (0.25%) and heat to have no effect on ich. Other studies say 0.5% to 1% salt can reduce mortality from ich but is not as effective as medication. UV sterilizers, even at low wattages, can help immensely to eliminate ich from the aquarium.
Established filters have thousands of little carnivorous critters in them which eat the infectious ich stage (the “theront”), so the filter is very important. The net result of this filter “medication” is that if you have a long-established aquarium filter with plenty of brown “gunk” in it, it is perfectly OK to do absolutely nothing for the ich. It will simply go away on its own in a week or two.
Because ich will go away in an established aquarium, there are at least 55 “treatments” currently “absolutely guaranteed” to stop ich. There is an old saying in science: “correlation does not imply causation”. ANY treatment of ich in a tank with an established filter will work. The ashes from the cremation of a dead squirrel will work to remove ich in a tank with an established filter
This article is a review of all the effective treatments for ich and the research articles on these treatments. It is very long and boring. I only recommend it for people who are nerds like I am.
Research on Ich Medications
Per the aquaculture experts at the universities and myriad research papers formalin/malachite green in combination (Ich-X, Rid-Ich Plus, White Spot Remedy and Mardel QuickCure) is THE treatment of choice for ich. These well done scientific University research papers with controls include:
- Tieman et. al. 2001
- Mamuna et. al. 2019
- Maceda-Viega et. al. 2014
- Duborow et. al. 1998
- Leteux et. al. 1972
- Rintamaki-Kunnunen et. al. 2005
- Bauer et. al. 1969
- Wahli et. al. 1993
Malachite green, methylene blue, and straight formalin (NT Labs Koi Care Formaldehyde), copper (Cupramine, Copper Power, Copper Aide or Copper Safe) and 5,000 to 10,000 ppm salt are somewhat effective against ich by the some of the same research.
In the U.S. formalin/malachite green is the best medication to use for freshwater aquariums, period. But in Europe formalin is banned. So one needs to look at alternatives. And some are not comfortable using formalin/malachite green as they either don’t like medications or they are not comfortable with formalin/malachite green as it can easily be overdosed and will kill fish if overdosed.
The Seminal Work on Ich Medications in the Aquarium
The best study by far on ich medications is the paper: “Treatments for Ich Infestations in Channel Catfish Evaluated under Static and Flow-Through Water Conditions,” Darlene M. Tieman and Andre W Goodwin, University of Arkansas at Pine Bluff, Department of Aquaculture/Fisheries, North American Journal of Aquaculture 63:293–299, 2001, American Fisheries Society,. Here is the list they found:
This study did not test formalin/malachite green in combination but they hit virtually every other medication proposed for ich. They found the following to be reasonably effective medications: malachite green, methylene blue and 25 ppm formalin. One can reasonably conclude that formalin/malachite green is a good combination to use with freshwater ich.
This study found copper to be effective at preventing new infestations but it did poorly in treating fish which already had the disease.
The following medications and treatments simply didn’t work:
- Increasing the water flow
- Raising the temperature
- Chloramine T
- Hydrogen Peroxide
- Potassium permanganate
- Salt (sodium chloride) at 3,000 ppm
There are many other studies on individual treatments for ich. Almost ALL these studies support the findings of this seminal paper. The major divergence is that there are several well done studies which say salt somewhat works (see below).
Mythbuster: Research clearly says that heat is NOT effective against ich.
Note that many get confused by the terms “static” and “flow” on this list. It took a phone call to the fishery to clear up the meaning. These catfish are in VERY heavy stocking in concrete sluiceways with water from a creek being put into the sluiceways in what amounts to a high flow continuous water change system. This is why they can do this with no water filtration.
There was a push to reduce the water usage. This test was run in unfiltered glass aquariums. Some of the aquariums had “flow” where water was flowed into and out of the aquariums at about 20% per hour. I.e. roughly every six hours there was a 95% water change in the “flow” aquariums. There was no such “flow” in the “static” aquariums.
What this research says is that VERY frequent (like once every 12 hours) 95% to 100% aquarium water changes will slightly help with ich in some situations. Per the phone call the researchers concluded that they could not reduce the turn-over rate without getting more fatalities with ich. More on this topic below.
Formalin and Malachite Green Research
There are several formalin/malachite green medications widely available which will treat ich. They include: Ich-X, Rid-Ich Plus, White Spot Remedy and Mardel QuickCure. If Ich-X is used per the directions, it ends up being 22 ppm of formalin and 0.13 ppm of malachite green in the aquarium
From all the research papers it appears that formalin is the best medication to kill the free swimming infectious theronts in the water column. But formalin has some problems:
- It is rapidly converted to harmless formic acid by the bacteria in most filters. At 65 degrees F (18 C) 50% of it converts in 18 hours. At 75 degrees F (24 C) 50% of it converts in 12 hours, At 85 degrees F (29 C) 50% of it converts in 8 hours. This conversion is somewhat unpredictable.
- It is poisonous in overdoses. At 65 degrees F (18 C) it kills some species of fish at 150 ppm. At 75 degrees F (24 C) it starts killing at 75 ppm, At 85 degrees F (29 C) it can kill at 50 ppm. Again, this is very unpredictable with some species having much more tolerance than others.
So formalin needs refreshing on a schedule dependent on temperature and it needs to be dosed according to temperature. The directions on most formalin/malachite green medications appear to be for 75 degrees F with treatment every 24 hours. So we do NOT recommend raising the aquarium temperature if you are using a formalin medication. You COULD kill some fish species. If you have an aquarium with a temperature over 80 degrees F (26 C) we recommend a half dose of formalin/malachite green medication every twelve hours.
One study looked at using formalin/malachite green at 77F (24C) with dosage being every 48 hours. The treatments did NOT work because the 48 hour time period was too long between doses (“Heavy Infection of Ichthyophthirius Multifiliis in Striped Catfish and its Treatment Trial by Different Therapeutic Agents in a Control Environment”, Mamuna, 2019). So frequent dosing is important, especially at higher temperatures.
This time dependency of treatment is supported in the literature not only due to the life of formalin but also due to the life cycle of the ich organisms. The life cycle duration of ich is temperature-dependent; treatments must be daily (every 24 hours) when temperatures exceed 77F (24C) or on alternate days when temperatures are 66 to 76F (19–23C) (Durborow et al. 1998) at a minimum due to the life cycle.
Malachite green works synergistically with formalin in that malachite green appears to attack the skin cyst trophonts and the substrate tomonts. This is not surprising. Aniline dies such as malachite green penetrate and stain all sorts of materials quite well. Malachite green does also have two problems:
- It is poisonous at a roughly level of about 0.3 ppm
- It stains everything blue and the stain lasts a long time
So all the various formalin/malachite green medications work well if the dosing directions are carefully followed. “More is not better” with formalin/malachite green.
Note that formalin is NOT absorbed from water with activated carbon. But malachite green is absorbed from water by FRESH activated carbon. So if one has carbon in a filter where the carbon is less than two weeks old, the carbon needs to be removed for the treatment. If the carbon is more than two weeks old just leave it be.
It is important NOT to follow the directions that come on the medication and remove or modify the filtration. Neither formalin, malachite green or formalin/malachite green interfere with the beneficial bacteria in the filter. Collins et al. (1975) demonstrated that formalin (25 mg/litre), malachite green (0.10 mg/litre) and formalin and malachite green (25 mg/litre plus 0.10 mg/litre. respectively) did not interfere with nitrification. Methylene blue did stop nitrification.
“Effects of Parasiticides on Nitrification”, Collins, et. al., 1975.
“Treatment of four recirculating systems with a single dose of methylene blue at 5mg/liter resulted in complete cessation of nitrification for 16 days as evidenced by a rapid rise in ammonia and stable nitrate concentrations. The therapeutic use of methylene blue in recirculating systems is contraindicated. Treatment of the systems with therapeutic levels of formalin, malachite green, formalin and malachite green in combination, copper sulfate, potassium permanganate, and sodium chloride had no effect on nitrification.”
Now I’m going to go out on a limb here with a caveat. Collins tested well established filtration systems, systems which had a lot of “brown gunk” in them. The total biological load in the systems was probably quite high. If one is treating a tank with little brown gunk in the filter (either relatively new or just cleaned), then I suspect that one will need to do a fish-in cycle after treatment with formalin.
Formalin/malachite green has a very long history of research which show it to be effective against ich. Leteux and Meyer 1972 did research which showed channel catfish with infestations of ich could be successfully treated with 0.05 mg/L malachite green mixed with 15, 25, or 50 mg/L formalin. Goldfish were treated successfully for infestations of ich with a mixture of up to 0.2 mg/L malachite green and 33 mg/L formalin.
Another formalin and malachite green reference is “Treatment of Ichthyophthiriasis after Malachite Green”. Rintamäki-Kinnunen e. al., University of Oulu, Finland, 2005:
“White spot disease (ichthyophthiriasis), caused by Ichthyophthirius multifiliis, occurs in both wild and cultured fish. Without any preventive treatment it may cause high mortality among both juvenile and adult fish (Elser 1955, Valtonen & Keränen 1981, Majeed etal. 1984, Wurtsbaugh & Tapia 1988, Traxler et al. 1998). Many chemicals have been tested for preventing the disease, e.g. malachite green, malachite green in combination with salt or formalin, formalin, chloramine-T, potassium permanganate and copper sulphate (Johnson 1961, Ljunberg 1963, Prost & Studnicka1972, Cross & Hursey 1973, Schachte 1974,Straus 1993, Schlenk et al. 1998, Straus & Griffin 2002). Malachite green with formalin has been found to be the best alternative (Bauer et al. 1969, Wahli et al.1993, Rintamäki-Kinnunen & Valtonen 1997, Tieman & Goodwin 2001).”
Formalin is used by large public aquariums when their freshwater fish get itch (Hadfield, 2011). I suspect the aquariums do not use malachite green as they do not want the staining.
If one is in Europe formalin is not available. There are three medications which will work in place of formalin/malachite green: malachite green, methylene blue and copper (Cupramine, Copper Power, Copper Aide or Copper Safe). In Europe ESHA 2000 is a good formalin free ich medication which combines copper with some acriflavin dyes.
Sera med Protazol is interesting. It is a malachite green derivative which is not colored. There is no research I could find verifying that it is effective against ich. Since the killing action of aniline dyes seems to be connected with the fact that they dye things the author simply cannot recommend this product.
Using Copper to Treat Ich
Some of the commercial copper medications which work include Seachem Cupramine, Copper Power, Copper Aide or Copper Safe. If one can’t get these medications one can get copper sulfate as “blue vitriol” in the drain cleaner section of the hardware store.
Copper has what is called limited selectivity. Copper medication kills invertebrates (ich, costia, velvet, etc.), it has much less of an effect on fish. It is recommended not to use copper in any aquarium which has shrimp, snails, or crayfish.
To calculate the amount of copper to use technically one needs to know the “total alkalinity” of the water. This includes the amount of carbonate AND hydroxide in a given water supply. This is not easily done. So one has to approximate “total alkalinity” by using “alkalinity” or KH, carbonate hardness. That’s what we do below and it probably is good ninety percent of the time.
Copper sulfate, CuSO₄, treats most protozoan parasites on fish at a rate calculated by dividing the water’s alkalinity (KH) by 100 and using that concentration in ppm for the copper sulfate treatment. If the alkalinity is measured by dKH (typically a number between 1 and 20) the alkalinity needs to be multiplied by 18 before doing the calculation.
For example, aquarium water with a total KH alkalinity of 80 ppm (dKH of 4.4 or 80/18) would need 0.8 ppm (80/100 x 1 ppm) copper sulfate (CuSO₄). If the KH (alkalinity) is over 250 ppm (14 dKH), do not use more than 2.5 ppm of copper sulfate. It is typically not recommended to use ANY amount of copper when the water is below 70 KH, or 3 dKH or lower.
This is a very small amount of copper sulfate. In a 100-gallon aquarium one part per million (1 ppm) is 0.38 grams. A typical 100-gallon aquarium with an alkalinity of 80 ppm or a GH of 80 (4.4 dGH) would only need 0.3 grams (0.38 x 0.8 = 0.3 grams) of copper sulfate. A twenty gallon would need only 0.06 grams.
It is important to keep up the therapeutic level of the copper for a considerable length of time. All signs of ich should be gone for at least a week before stopping treatment. Many suppliers make cheap test kits for copper. Use them.
Many “experts” say copper kills bacteria so don’t run the biological filters when using copper medications. This is simply wrong. If copper killed bacteria, solutions of copper would be used as a disinfectant. No one has ever used solutions of copper as a disinfectant. And if you turn off the filters you remove the most effective treatment there is for ich.
Collins et al. (1975) demonstrated that copper sulfate (1 mg/litre) did not interfere with nitrification. But copper will kill shrimp very rapidly. It also supposedly kills snails. Note I have tried to get rid of snails using copper and it didn’t work.
Copper sulfate is often used to control ichthyophthiriasis because of its effectiveness, long life and low cost (Straits 1993; Schlenk et al. 1998), but the chemical can be extremely toxic to fish in water with low alkalinity (Straus and Tucker 1993; Wurts and Perschbacher 1994; Perschbacher and Wurts 1999). The typical treatment rate for aquaculture ponds is 1 mg/L copper sulfate for every 100 mg/L total alkalinity (Macmillan 1985; Tucker and Robinson 1990).
Per Schlenk, 2011:
“Ichthyophthirius multifiliis is a protozoan that may infest and significantly damage cultured fish species. The purpose of this study was to measure the efficacy of copper sulfate in treating ichthyophthiriasis. Fingerling channel catfish Ictalurus punctatus exposed to at least 2,000 theronts of I. multifiliis per liter of water developed consistent infestations of I. multifiliis (20 or more trophonts on the dorsal surface of the head of the fish). Infestation was observed in untreated controls at day 5 after exposure and mortality occurred after day 10.
Coexposure studies with theronts and different concentrations of copper sulfate revealed that all theronts were killed at concentrations greater than 0.05 mg/L. To determine the effect of copper sulfate in the treatment of ichthyophthiriasis, fish were exposed to the parasite until trophonts were observed (day 5), and they were subsequently treated with copper sulfate. The lowest effective concentration of copper sulfate for treatment of ichthyophthiriasis (i.e., after infestation was observed in the fish) was 0.4 mg/L. To assess the effects of various water quality conditions on copper treatment, total suspended solids (TSS) and pH were varied during treatment of ichthyophthiriasis.
Concentration of TSS was inversely correlated to the efficacy of copper sulfate for I. multifiliis infestations, whereas no relationship was observed between pH and efficacy of a single copper sulfate dose. The results indicated that copper sulfate can be used to treat ichthyophthiriasis at concentrations of 0.4 mg/L for at least 5 days under the specific water conditions used in this study (pH, 7.45 ± 0.26; temperature, 20.5 ± 0.7°C; alkalinity, 176.6 ± 28.1 mg/L as CaCO₃) and that efficacy of copper sulfate was affected more by TSS concentration than by pH.”
So copper is relatively effective against ich per this research. Note this research used one fifth the concentration of copper sulfate as other researchers and still found it to be effective.
Salt as a Treatment for Ich
If one is dead set against using any “chemicals” in their aquariums and wants to use a “natural” approach, salt (sodium chloride) is reasonably effective at a dosage of one to two cups of salt per ten gallons of water (5,000 to 10,000 ppm). This is based on the following research:
Research which showed salt to be somewhat effective against ich:
- 5,000 ppm salt reduced ich mortality with silver perch, Murry cod, golden perch and dewfish (Selosse et. al. 1990)
- 10,000 ppm salt eliminated ich in mollies (Maceda-Viega et. al., 2014).
- >2,500 ppm salt killed ich theronts (Aihuaet. et. al., 2001; Shinn et al. 2005; Lahnsteiner et. al., 2007)
- 5,000 ppm salt reduced infestations (Selosse et. al., 1990; Miron et al. 2003; Balta et al. 2008)
- >2,000 ppm salt partially controlled ich in silver perch (Mifsud al., 2008)
- 4,000 ppm salt partially controlled ich in silver catfish (Miron et. al. 2008)
- >5,000 ppm salt partially controlled ich in trout (Aihua et. al. 2001)
- 10,000 and 20,000 ppm salt partially controlled ich in striped catfish (Mamun, 2019)
Research which showed salt to be ineffective against ich:
- 1,000 ppm salt did not control ich in silver perch (Mifsud al., 2008)
- 3,000 ppm salt was not effective at eliminating ich in channel catfish (Tieman et. al. 2001).
- 15,000 to 20,000 salt baths for 20 to 60 minutes did not reduce ich (Lahnsteiner et. al., 2007; Balta et al. 2008).
A level of 5,000 to 10,000 ppm of salt is safe for all fish, including corydoras and other Amazon fish. Treating with salt, including why table salt is fine for an aquarium fish medication, is analyzed in depth in this link:
Now the use of salt as a treatment for ich has a caveat. All the studies listed above had results which were along the lines of “Salt only had 40% mortality while the control (no salt or medication) had a 100% mortality”. This is why salt is not the treatment of choice by the experts. Salt is not as effective as formalin/malachite green or copper.
Water Changes and Ich
One approach to treating ich is simply water changes. The math with this approach is interesting.
Let us take an aquarium that is infected with ich and make some assumptions. Let us assume there are 500 tomants (which live three days) per day in the substrate producing 400 ich theronts when they burst and die. This is a loading of 200,000 free swimming infectious theronts per day going into the water. At 78 degrees these theronts will live for two days. Let us say that under “poor” case conditions (i.e. with only limited filtration) the 200,000 theronts will produce 1,000 tomants in the substrate (4 days later) to continue the process, 500 the first day and 500 the second day of the theronts lives. Then a chart can be set up by generation:
So, water changes can “assist” in control of ich. But the water changes need to be large and often. Obviously 25% per day will not do very much, allowing the ich disease to progress, On the other hand, 95% per day will be extremely helpful, significantly reducing the infection. Note that 95% water changes do NOT harm the fish. The idea that large water changes harm the fish is just a commonly parroted myth.
Journal Support for Water Changes and Flow Rates as Ich Treatments
There was an interesting article on treating ich. It looked at flow (“water velocity”) and turnover (water changes) as variables in the treatment (“Flowing Water: An Effective Treatment for Ichthyophthiriasis”, Leo R. Bodensteiner et. al., 2011).
There were juvenile catfish in raceways with very heavy stocking (easily 50 times the stocking density of a typical aquarium). They tried formalin with four hour baths four days a week but that didn’t work (formalin only kills the ich theronts and as such must be in the water 24 hours a day to be effective).
But when they started turning over the water (i.e. changing the water completely) more than twice an hour the ich and increased the flow rate, the ich infection went away. In aquarium terms this would equate to changing 50% of the water every 15 minutes or 95% every 30 minutes. But the fish density in these raceways was very high. If one corrects for the density by multiplying 15 minutes by 50 you come up with a 50% water change every twelve hours or a 95% water change every 24 hours controlling the ich. This would support that idea that frequent large scale water changes can HELP control ich in an aquarium.
This research was a bit flawed in that it simultaneously increased BOTH the flow rate and the turnover rate. So it is difficult to to say which variable is more important in controlling ich. But be increasing both the flow rate and the turnover rate they eliminated ich completely from their catfish. The flow rate they used was 85 cm/minute. This is NOT a high flow rate in an aquarium. Any wavemaker will create flow rates much higher than that. So it would appear that adding one or two wavemakers to an aquarium with ich is a wise thing to do.
It would appear that the ich theronts has difficulty attaching to the skin of the fish if the flow is high over the skin of the fish. Again, this was one piece of research that had some flaws so I hesitate to say that adding a wavemaker will be a cure for ich. But it is definitely worth a try if one is faced with an ich outbreak where the filter are new and one cannot get formalin/malachite green.
UV and Ich
Note a flow through UV sterilizer can kill the ich theronts and control an ich outbreak almost as effectively as an established filter.
“Ultraviolet Light Control of Ichthyophthirius multifiliis Fouquet in a Closed Fish Culture Recirculation System”, Gratzek et. al. University of Georgia,
“Analysis of the mortality patterns of the fish exposed to I. multifiliis demonstrated that the incorporation of UV light in an aquarium system significantly (F< 0-005) reduced deaths. It was determined that the 82-81% death rate in the control group was significantly greater than either the 1-33% death rate when one UV lamp was used in the system or the 0-7% death rate when two lamps were used.”
Because of something called “reciprocity” in an aquarium UV setup, UV in relatively small doses will kill the ich organism and is very useful in the treatment of ich. More about this can be found in the following web page:
Ich in more Depth
Ich is the most common fish disease and warrants a more in-depth discussion. The following chapters are devoted to this common fish disease:
Aquarium Science Website
The chapters shown below or on the right side in maroon lead to close to 400 articles on all aspects of keeping a freshwater aquarium. These articles have NO links to profit making sites and are thus unbiased in their recommendations, unlike all the for-profit sites you will find with Google. Bookmark and browse!