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Retired Mod
Feb 15, 2002
Great Barrington, MA

What is it?
Ich is a protozoan parasite scientifically known as Ichthyophthirius multifiliis. Ok what the heck does that mean, right? Basically ich is a parasite that attaches itself to a host, in this case your fish, and feeds off of it. It has three life cycles which I will explain so that you can better understand how to treat it. Don’t worry too much if you come to the conclusion that your fish have this disease as it is unfortunately common but very treatable and often can be treated with out any casualties as long as it is caught early enough. Once it spreads into the gills of the fish or causes secondary bacterial infections is when it will become the hardest to treat.

How do I know if my fish have ich?
Most of the time the aquarist realizes that their fish have ich when they notice little white spots all over their fish’s bodies and fins that kind of resembles little grains of salt. Unfortunately when it does become visible your fish has probably been suffering with it for some time as this is the final stage of the parasites life cycle. There are some earlier signs to be aware off and watch out for. Most likely the first sign of any infection will be clamped fins and abnormal swimming habits and while this isn’t a sure symptom of ich it is a good indication that something is wrong and that you should be looking for what it is. The second symptom is most often flashing or scraping which is where you fish rubs up against something like a pot or gravel almost like it is trying to scratch itself which is in fact what it is doing because the ich parasite is irritating it. The final stage of infection will be as said earlier small white spots all over the fish that will appear raised up almost like grains of salt.

Understanding how Ich Spreads
Ich is a single cell parasite that has a three stage life cycles. This gets a bit scientific but I think it’s useful in knowing how to treat it. The organism is usually discovered in the Trophont stage which is the adult stage of the parasites life. This is the only stage that it is visible to the naked eye as white spots on your fish. There is a bit of debate on this but it is believed that the ich is not vulnerable to medications in this stage. Once the organism finishes this stage of their life they drop off of the fish and fall into the substrate (gravel) of your tank and become encysted in a free living dormant stage. This stage of the organism’s life is called the Tomont stage. The cyst will be invulnerable to medications. The organism will stay in the dormant encysted state anywhere from several hours to several days depending on the water temperature. (The warmer the water the quicker it will divide which is what you want so the medication can kill the new organism). It will divide into 200-800 larvae called Theronts. These new organisms do not have long to find a new host before they die. The fish usually pick up the new parasites when they flash on the substrate of the tank continuing the cycle. This is the stage when medications definitely kill the ich so remember even if you no longer see it on your fish finish out a full week of treatment because it could still be in the water

Treatment Options
There are several different options when treating ich. I will go over them here. If you know of any others let me know and I will add them.

The first, safest and in the authors opinion best treatment method is simply salt. You don’t need any special salt just so long as it’s NaCI salt and not something like Epsom salt or marine tank salt. If you’re not sure just purchase some aquarium salt from your fish store. The method for treating is relatively easy. The common recommended dose for treating ich is 2 tsp per gallon of water. It’s not recommended to put the salt right in the tank. You should mix it in with water so that it dissolves and then add the salt water into the tank. I recommend that you add about a quarter of the salt mix every few hours so that you don’t shock your fish as badly. You only do this once not everyday like with other ich medications. Salt does not evaporate or dilute over time in the water. The ich will probably look like it is getting worse for the first few days while you’re waiting for the salt to have its effect on in. If the ich does not look like its getting better after 5 days you will want to increase the dose by another 1 tsp per gallon. If you are keeping tropical fish I would recommend slowly turning the heat up to 86 degrees to help quicken the life cycle of the cyst which will not be affected by the salt. If you are keeping goldfish or other cool water species I would go to 74-76 degrees. Some people will tell you that 80 is ok for cool water but this really brings them undo stress. 74-76 will speed up the cycle of the organism enough that it should be killed off out in a week’s time. Remember heat is not necessary to kill ich the salt or medication will do it on there own but increasing the temperature will quicken the life cycle of the ich organism. If you keep any invertebrates or very fragile species you may want to consult an expert of the species to make sure that salt will not harm them. I would wait about seven days before doing another water change so that the salt has time to wipe out the life cycle of the organism. When you are done treating for ich I wouldn’t worry about doing a massive water change just your normal maintenance and the salt will be diluted out over time. Once you do a water change it is not necessary to add more salt back to the tank. If you do a water change during your treatment or want to continue treatment after seven day’s you will need to measure out how many gallons you take out of tank. Once you have removed the amount of water that you feel is sufficient for your water change refill the aquarium with fresh water equal to what you removed in old water. Then re-dose the tank with salt equal to 2 tsp per gallon of water that you removed. For example if you removed 20 gallons of water then you will want to add 40 tsp. of salt back into the tank.

The second treatment is a commercial ich medication usually containing malachite green, formalin, formaldehyde or a combination of the three. These medications are some what strong and should not be used with scaleless fish such as Loaches and Puffers. You would also want to avoid them if you keep delicate or fragile fish. Malachite Green will stain your silicone in the seams of your tanks a blue green color so if this is something that will bother you then I wouldn’t use this method. For Tetra’s always use half dosage as it will adversely affect them in any higher concentrations. This will most likely be listed on the bottle. As far as other dosage amounts you have to read the bottle of treatment that you buy as they all vary from manufacturer to manufacturer. You can also raise your tank temperature with these medications to speed up the life cycle of the ich. As with all medications if you use activated carbon you will want to remove it from the filters during treatment and then after you finish the treatment do a water change and replace the carbon to absorb any remaining medications.

Another treatment that will kill ich and anything else in your tank besides the fish is copper or copper sulfate. I do not recommend that you use this medication. It hasn’t been proven that there are any long term side effects to fish but it is often speculated. It can also be very hard to remove all of it making it impossible to keep invertebrates for, in some instances, years. I really recommend trying other treatments before you resort to copper. They are much safer and just as effective.

A stressed fish will cause an ich outbreak?
No it will not. The only thing that will cause an outbreak is the parasite itself coming into your tank on a new inhabitant or possibly a plant. There are instances where fish will develop partial immunities to pathogens in there water systems so it is possible that your fish may have lived with ich for a while with out really showing any signs of it and once something goes wrong with the water conditions there will be an outbreak that you notice. I believe this is how this misunderstanding came about.

I have been treating ich for over a week and it is still present in my tank. What am I doing wrong?

There are many different strains of ich and some of them are quite resistant to medications. The only real recommendation that I can give is just to continue to treat the tank until you no longer notice spots on your fish and then continue for another week to make sure that all the other stages of the cycle are killed off.

I’m pretty sure the ich is gone but my fish still seem sick.
Ich especially bad cases can leave the fish vulnerable to secondary bacterial infection. This doesn’t mean that your fish have another infection. All treatments for ich will cause stress to your fish. They could be acting strange do to the effects that the treatment had on them. If your fish don’t seem to be improving and there is no more sign of the parasite then you should seek advice about what type of bacterial infection your fish may have. A broad spectrum antibiotic is usually best for treating secondary infections but you should make sure that your fish do in fact have secondary infections before dosing an antibiotic.

Should I move my fish to a quarantine tank to treat them?
No, once the organism is established in your tank the whole tank must be treated to eradicate it. This is not to say that you shouldn’t quarantine new fish that you have just purchased.

I heard I should use salt in conjunction to treating with a commercial medication.
This is not advisable. Your fish will be under enough stress from just one of the many treatment methods and combining them will only increase it. I’m sure some people have had success doing this but don’t feel I can recommend to you that it be done as more stress can contribute to more fish loss.

Someone told me all I really need is just heat to eradicate ich.
While most strains of ich are unable to survive at temperatures above 84 degree’s there are strains out there that have made it up to 90 degree’s Another thing to remember is unless you can be certain that all areas of your tank are staying above 84 degrees there is a chance that a small corner some where in the system could stay cooler and the ich would be able to survive. So yes heat alone can kill ich but I recommended using some thing in conjunction with it just to be sure.

I thought high heat could be harmful to my fish?
It can be. The higher the water temperature the less oxygen saturation there is in it. If you have very oxygen sensitive fish you may not want to raise the temperature at all or raise it but not as high. Remember heat is not necessary to kill ich the salt or medication will do it on there own but increasing the temperature will quicken the life cycle of the ich organism.

Pictures of freshwater ich

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