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Ich, also called white spot disease, is one of the most common protozoan infections affecting aquarium and pond fishes. The scientific name for freshwater ich is “Ichthyophthirius multifilis. The marine protozoan causing ich is Cryptocaryon irritans. Both organisms cause whitish spots, called “cysts”, to appear on the bodies and fins of the infested fishes.
DIAGNOSIS:
The usual way of diagnosing ich is by close observation of the infected fishes. The presence of small, (.5 to 1.0 mm) white dots (kind of like salt) scattered about on the fishes' skin. This is most easily observed around the tail or fins (especially if the fins normally clear). You can check this out by removing one of the spots and observing it under a microscope. Ich has a small micronucleus and a prominent crescent-shaped macronucleus.
LIFE CYCLE:
Ich is most often introduced into the aquarium or pond by adding new fishes or aquatic plants. Tomites which have only recently attached themselves to the host will not be readily visible. It is good aquarium and pond keeping practice to isolate any new fishes for at least four days under close observation. For tropical fishes, maintain a temperature of around 75° F (24° C). Check carefully for the presence of any tell-tale white spots appearing on the skin of the fishes and treat them accordingly. If no white spots are observed on tropical fishes within four days at this temperature, they can be moved from isolation. Remember, fishes maintained at cooler water temperatures (such as pond fishes) will require longer isolation times.
The visible stages of Ich are carried out within the host fishes' skin. The first stages are called trophozoites and are highly resistant to drug therapy. Trophozoites mature into trophonts and leave the host, falling to the bottom of the aquarium or pond. These mature trophonts release from 200 to 1,000 tomtits. These tomites move about looking for a host, which they must find within 2 to 3 days at 75° F (24° C) or they will die. Cooler temperatures will lengthen this time. It is this free swimming stage that is most vulnerable to treatment. It is important to note that these intermediate stages may also attach themselves to plants and be accidentally introduced into an aquarium or pond along with the new plants. Once the tomite attaches to the host, it matures and the cycle begins anew. The parasite forms a nodule under the skin or gill epithelium of the fish host. It constantly turns and moves under the skin, feeding on destroyed cells and body fluids. It continues to feed on the cells until it matures, causing damage to the skin tissue. This leads to osmotic stress, resulting in secondary bacterial or fungal infections.
PREVENTION:
As in many parasite-caused diseases the fish must be sufficiently stressed and susceptible to the parasite. Also, the parasites must be present in the aquatic environment. It is not uncommon for an aquarium population to have a low-level of ich infestation present but not be showing any signs of the disease. Then, once a new fish is placed into the system it develops the disease. Fish can sometimes carry the parasite and not actually be diseased. These carriers can shed the parasite into a new aquarium into which it is placed. If the fish in the new aquarium have never been exposed to the parasite, and they become stressed, they can develop the disease.
The health aquatic environment can play a major role in susceptibility to the ich parasites. High ammonia and nitrites severely stress a fish. Also long term nitrates above 50 ppm in freshwater or 30 ppm in saltwater can weaken the immune system in fish. Calcium is also often forgotten as an essential to fish health (including soft water fish such as Discus). Without calcium fish cannot carry out many osmotic functions and are more susceptible to disease, including ich infestations. For more information about Calcium and KH, please see this article: CALCIUM, MAGNESIUM, & KH
IN AQUARIUMS
A healthy, cycled aquarium with a steady temperature and a KH above 80 ppm is less likely to develop ich, or when it does, a healthy aquarium will have a less serious and more easily treatable infestation.
TREATMENT:
There are many ways to treat ich infestations in freshwater, less in saltwater, but not all treatments are equal or can be used for all types of fish or all aquatic environments. I will only discuss the options I prefer to use in my maintenance business or in my personal aquariums.
For freshwater a Malachite Green/ Formalin combination has generally been the most effective for moderate to severe infestations. “Quick Cure” is good product with this combination of medications. Malachite Green by itself as in “Nox Ich” is also effective in moderate infestations. Other treatments of note are copper sulfate and Quinine Sulfate or Hydrochloride. For scale-less or delicate fish use Malachite Green at half dose. The safest treatment for scale-less fish is Quinine Hydrochloride, but this is less effective than other treatments, although it can be combined with half strength Malachite Green for more effectiveness.
For mild to moderate infestations (even some severe) I also use “Medicated Wonder Shells” as these products have Malachite Green (lower levels safe for most delicate fish), acriflavin, and small amounts of methylene blue (not enough to affect bio filtration) and copper. What is best about these “Medicated Wonder Shells” is that they also add electrolytes, calcium and maintain a proper KH, which is very important for treatment with Malachite Green as this medication is more toxic at lower pH and KH.
One more treatment option is a hospital tank with a Sponge Filter and no gravel. Methylene Blue works well here, but so do ALL of the above treatments as well.
For saltwater Cryptocaryon I do not recommend Formalin. Malachite Green is relatively safe for saltwater fish and some invertebrates such as crabs and even some anemones, but definitely NOT for cephalopods. Malachite Green is not as effective a treatment as it is in freshwater applications for ich infestations. Quinine Sulfate or Hydrochloride is also relatively safe for most fish, but not invertebrates. Metronidazole can also be used for marine ich infestations and is safe for many invertebrates (NOT ALL! So use with caution), but again is relatively ineffective for ich (Cryptocaryon) treatment. Copper sulfate is still the most effective way to treat in Cryptocaryon saltwater, but copper (especially chelated) can be hard to remove from your system once used and is deadly to invertebrates. There is a marine version of the “Medicated Wonder Shells” which only contains Malachite Green, this product is mildly to moderately effective for marine ich (Cryptocaryon). For saltwater fish, prevention is still the best cure, such as UV Sterilization. Also a quarantine tank for new fish and a hospital tank for sick fish are also beneficial. If a hospital tank is available (bare tank with a sponge filter), a treatment with Methylene Blue and or copper is advisable.
By Carl Strohmeyer
www.americanaquariumproducts.com/Aquarium_Ich.html
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