Ich: Prevention and Cure
What is ich?
"Ich", or "White Spot Disease", is one of the commonest fish diseases and is caused by the cilliated protozoal parasite, Ichthyophthirius Multifilis. The parasites burrow into the fish’s skin to feed on its tissue and body fluids. Death is eventually caused by physical trauma, loss of fluid resulting in osmoregulatory imbalance, impaired breathing due to heavy infestation of the gills, or by secondary infections of bacteria or fungus entering through the skin lesions.
The visible symptoms of ich include:
tiny white spots scattered over the fish like grains of salt
slimy skin due to heavy mucus layer
frequent rubbing or flicking against the substrate or ornaments
abnormal swimming behaviour
lethargy and loss of appetite
fraying fins and/or cloudy eyes
The goldfish in the photograph at the bottom of this page displays classic symptoms of a heavy ich infestation.
Under the microscope, the parasite looks spherical or pear shaped. Its whole body is covered in fine hairs (cilia) which provide a continuous rotating movement, enabling it to move around. Its macronucleus is horse-shoe shaped and the micronucleus is spherical.
Ich has a distinct three stage lifecycle:
1. The mature parasites (trophozoites) dig themselves into the fish’s skin, forming visible white pustules, and begin feeding on the tissue and fluids.
2. Each trophont matures, breaks out of its pustule and settles at the bottom of the tank as a cyst coated in protective gelatin.
3. Inside the cyst the trophont performs a rapid series of cell divisions, generating as many as 300 new cells (tomites). These tomites are released and swim freely for up to 70 hours (3 days) seeking other hosts to parasiticise. Only about 15% actually succeed but this is enough to increase the infestation rapidly if left untreated.
The life cycle is temperature-dependent, however. It can occur in three to four days at 70 degrees F and up to five weeks at 50 degrees F. At lower temps, the parasite will remain dormant. Its optimum working temperature is 86 degrees F.
What causes ich and how can it be prevented?
Firstly, ich parasites actually have to be present in the aquarium or pond to cause an infestation. Some aquarists claim temperature fluctuations cause ich, but this is not so unless the organism is already there to begin with. (What actually happens is the fish get stressed by temperature swings thus decreasing the efficiency of their immune systems and allowing ich parasites to gain access).
Ich can be introduced into the aquarium via infected water, plants, substrates or fish. Some fish can in fact carry the parasite without actually ever being diseased themselves. These carriers shed the parasite into a new aquarium and expose other fish to it who may not have a natural immunity and thus become infected.
Therefore, there are some very simple precautions which can prevent ich being introduced:
Don’t buy any fish from a tank in which ich (or any other disease for that matter!) is obviously present.
Quarantine all new fish for at least a month before introducing them to the main tank or pond;
Don’t add any pet store water to your tank or pond: do the usual temperature and water chemistry adjustments for new fish in a separate bucket and then net the fish out to put it in the tank/pond, leaving the pet store water to be thrown away.
Disinfect any new plants, ornaments and substrates with a bleach or potassium permanganate solution before placing them in the tank.
The ich parasite can lie dormant for long periods in established ponds and aquariums or exist at a very low level of activity. Like most animals, healthy fish have a well-developed immune system so they are not unduly bothered by the odd lurking ich parasite or other disease. If they become stressed however then their immune system is compromised and ich may gain a foothold.
The best way to prevent this type of infection, therefore, is to ensure the fish is not exposed to stress; high ammonia, nitrites or nitrates, fluctuating pH or temperature, low dissolved oxygen content, cramped space or unsuitable companions will all stress the fish and may lead to an outbreak of ich which could have been avoided by good maintenance.
Some aquarists also recommend keeping tanks salted at a .1% level continuously to prevent ich. However, although ich parasites are indeed inhibited by salt, the slight potential benefit of this is, in my opinion, far outweighed by the risk of increased osmotic stress on the fish and the extra work that maintaining a salt level creates for you. A clean, well-run aquarium should not need constant salt.
How to treat ich:
If ich breaks out it is necessary to treat the main tank or the whole pond, rather than removing the afflicted fish to a quarantine tank for treatment. This is due to the ich’s lifecycle and limited vulnerability to medications; the ich will be present in all three of its stages by the time you notice any symptoms and so it will keep re-occurring at the source of infection if left untreated.
There are three main treatment options for ich:
An ultraviolet steriliser
Heat, salt and darkness
I will deal with each of these in turn.
Ultraviolet Steriliser: This is not an effective treatment, although some aquarists swear by it. The idea is that the steriliser kills the free-swimming tomites as they pass through it. It does indeed kill them, but unfortunately tomites can attach themselves to new hosts very quickly, and therefore do not all pass through the steriliser. It is therefore very difficult to completely eradicate ich by this method alone, although it is useful as an aid to slow down infestation.
Store Medications: Generally considered very effective against ich, although it is advisable to repeat the treatments several times to ensure all the parasites are eliminated (regardless of the ‘instant cure’ claims made by the manufacturers!). Common chemicals used in these preparations are Malachite Green, Formalin, Quinine (hydrochloride or sulphate) or Copper. These medications should be handled very carefully, especially Malachite Green and Formalin which are highly toxic to humans. Wear gloves, don’t breathe in the fumes, don’t get any into your eyes or on your skin. They can affect the tank’s cycle so it is wise to test the water parameters regularly during treatment. They are also not good for plants and invertebrates (e.g. snails) so remove these from the tank before treatment. Malachite Green can also stain the interior of the tank, especially the silicone sealant. How do these medications work? They interfere with the internal workings of the parasite cells; Malachite Green inhibits cell respiration, for example, thus preventing the cell from achieving essential metabolic functions.
Heat, salt and darkness: This is surely one of the most hotly debated topics in fishkeeping! The suggested treatment procedure is as follows:
gradually increase the tank’s temperature to 80 degrees F.
add salt to a solution of 3 teaspoons per gallon (in increments of 1 tsp per gallon every 12 hours).
keep the tank in darkness by switching the light off and covering it with cloth or paper.
The theory behind how this treatment works is this:
Increasing the temperature to 80 degrees F speeds up the ich lifecycle to a few days and therefore speeds up the rate at which the tomites are killed off by the salt. It also boosts the fish’s immune system, helping it to fight off the disease.
The salt raises the salinity of the water to a level beyond the the tomites’ osmoregulatory tolerance, causing them to burst. Also, the increased salinity stimulates the fish to produce a slightly thicker slime coat, helping to prevent re-infection and secondary infections.
Ciliated protozoans cannot find new hosts easily in darkness and therefore more of the tomites die before they can latch on to the fish.
There seems to be good evidence, judging by the many stories related by people who have tried it, that this method does successfully cure ich.
However, many aquarists argue that it is an unsuitable, even dangerous, treatment because:
Raising the temperature to 80F reduces the oxygen level in the water which can make it more difficult for the fish to breathe.
Higher temperatures encourage the rapid growth of bacteria and fungus, putting the fish at increased risk of secondary infections.
Higher temperatures speed up the rate at which the ich reproduces and therefore places more stress on an already vulnerable fish population.
Coldwater fish such as goldfish will be put under more stress by a tropical-level temperature.
Such a high level of salt places osmotic stress on the fish as well as the ich tomites, so if the fish is badly infested – and therefore already struggling to control its osmoregulation - then this might be enough to kill it.
There is no real evidence that darkness inhibits cilliated protozoans.
Having read around extensively, I believe these arguments are not without some justification. Higher temperatures DO decrease oxygen levels; salt DOES place osmotic stress on fish, for example.
However, as with any treatment, the fish’s primary needs must be weighed-up: is the treatment going to harm the fish more or less than the disease? Will it harm the fish more or less than using store medications? Is there anything that can be done to ameliorate the risks of a chosen treatment?
Given how serious ich can become, and given how aggressive some medications such as formalin and copper can be in the tank, then I would not say that the heat and salt treatment is a poor option in comparison. Plus, there are things the fishkeeper can do to minimise some of the drawbacks: decreased oxygen levels can be resolved by increasing aeration in the tank, for example, and the temperature and salt can be increased gradually so avoid stressing the fish. And darkness certainly isn’t harmful! And, of course, some of the risk factors are counter-balanced naturally by the fish itself: yes, a higher temperatures increases bacterial activity, but it also sends the fish’s immune system into top gear, thus giving it extra protection against the bacteria.
In conclusion, I would say that store-bought medications carry equal benefits and risks in treatment of ich; it is up to each individual fishkeeper to decide which is the best option for their fish, because only they know their particular dispositions. Some goldfish seem very uncomfortable with an increased salt level while others are fine with it for example.
However, to use the old cliché: prevention is the best cure of all!
Post edited to include the photograph of a common goldfish with ich. The photo is reproduced with the kind permission of Muffysgurl.