Treating ich (white spot disease)




white spot disease

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Ich, also known as white spot disease or ick, is a very common fish disease that almost every aquarist will unfortunately encounter sooner or later. If there are white spots on your fish, you might be dealing with ich as well. 

Keep reading for everything you need to know about identifying and treating ich and how to prevent ich in the first place!

What is ich (white spot disease)?

Ich is a fish disease caused by a protozoan ectoparasite known as Ichthyophthirius multifiliis. A massive outbreak can quickly occur, especially if the immune system is already compromised by factors like bad water quality. Just one new fish carrying the parasite can infect all of its tankmates and treatment can be quite difficult due to the parasite’s life cycle. As the parasites feed on the fish it will grow increasingly weak.

If left untreated the disease will eventually be fatal, either due to increased susceptibility to secondary diseases or damaged gills. Luckily there are ways to treat your fish, though it’s important to start treating in time and not wait too long.

Identifying ich (white spot disease)

If you’re reading this article, you’re likely dealing with a diseased fish showing one or multiple suspicious white spots. There are multiple diseases that cause white spots, but fortunately ich is not difficult to identify at all.

  • Fish with ich will show multiple white spots. If the disease has reached a more advanced stage, your fish might be completely covered. If you’re only seeing one spot, you’re likely dealing with something else.
  • Ich is extremely easily transferred from one fish to another. A telltale sign of the disease is seeing multiple infected fish.
  • Ich looks like small salt granules. The spots will be tiny, slightly raised and not very fuzzy. If your fish has one or multiple larger fuzzy spots, you might be dealing with a fungal outbreak instead!
  • A fish with ich might show symtomps like “flashing” (strange, quick movements in an attempt to remove the parasites), lethargic behavior and labored breathing.
white spot
white spot by fjp

Treating ich (white spot disease)

When dealing with one or multiple fish that have been infected with ich, it’s important to start treatment as soon as possible. There are three methods to treat ich: two natural methods and the “chemical” method, medication. Except if you’re treating with medication, it’s a good idea to do daily water changes (25-50%) when battling ich.

Keep in mind that because of the lifecycle of this parasite the infection isn’t necessarily gone when you stop seeing white spots. Depending on the temperature of your tank, you might need to treat for quite a while longer.

Treating ich with high temperatures

The first thing you will want to do after diagnosing your fish with ich is to raise the temperature of your tank. This speeds up and disrupts the life cycle of the parasite, and, if temperatures are high enough, kills it. A temperature of 85 °F/29.5 °C or higher is usually recommended to kill ich, though obviously you should be very careful when turning the heater that high. Not all fish can withstand these temperatures and there should always be enough time for them to acclimate.

A crucial factor here is aeration: warmer water contains less oxygen and since ich can damage the gills, the last thing your fish need is even more difficulty breathing. Run one or multiple air stones or place an internal filter at the surface to agitate the water.

Ichthyophthirius multifiliis
Magnified view of Ichthyophthirius multifiliis by usfwspacific

Treating ich with salt

While warmer water alone can be enough to end an ich outbreak, you’ll often need to take extra measures. Like many other fish parasites, ich can be killed using plain old salt while many freshwater fish can withstand much higher salt rates than you might think.

If you’re planning to treat with salt, there are a few things to keep in mind. The salt in your kitchen cabinets is unfortunately likely not suitable, as it almost always contains iodine and/or anti-clumping agents. You could be looking for pure NaCl with no additives, like aquarium salt or dishwasher salt. Most fish with scales can handle a salt treatment just fine, but scaleless fish like loaches usually won’t react well to it at all. If you’re not sure, do some reasearch before adding any salt!

To treat an infected aquarium with salt, add about a tablespoon per 5 gallons. To do so, dissolve the salt crystals in some warm water and slowly add this to the tank, giving your fish time to acclimate. Be sure to add a proportionate amount of new salt when you do a water change.

Treating ich with medication

If neither salt nor high temperatures seem to be doing much to stop the ich outbreak there is one other option: using medication. Ich medication is available from many different brands and not too expensive. However, there are a few things to keep in mind if you’re intending to use it.

Many brands promise to eradicate the parasite within a very short time period; due to the life cycle ich goes through, this is not possible and you’ll actually have to treat for a longer time. Ich medication might also be unsafe for invertebrates like snails and shrimp, so be sure to check before administering it if you keep any inverts in your tank. Lastly, be sure to keep up the higher temperatures while treating with medication. This helps speed up the parasite’s life cycle, which means you won’t have to treat as long.

Preventing ich (white spot disease)

If you’ve managed to succesfully treat all your fish with ich, you’re likely wondering how to make sure all of it won’t happen again. The possibility of introducing something nasty into your tank is always there, but there are definitely some things you can do to lessen the chance of a new outbreak!

  • Keep water quality high. Bad water quality is very stressful to fish and weakens their immune system, making them more vulnerable to diseases like ich. Always make sure your tank is not overcrowded and fully cycled. Do regular water tests with a liquid test kit such as this one.
  • Always quarantine new fish. Stressed fish that have just been through transport are likely to be carrying ich or other diseases. Set up a quarantine tank to observe and possibly treat sick new fish in. Don’t buy fish from tanks or tank systems at the store that also contain sick tankmates, as it’s likely that all the fish are already infected.
  • Don’t put stuff from other aquariums in your tank (without cleaning!). Always clean new plants, don’t use the same equipment for multiple tanks, don’t let any pet store water enter your aquarium.

If you have any more questions about identifying, treating and preventing ich or want to share your own experiences with this pesky parasite, don’t hesitate to leave a comment below. Happy fishkeeping!

Cover photo: Ichthyophthiriose.JPG by Thomas Kaczmarczyk

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5 thoughts on “Treating ich (white spot disease)”

  1. I have a 700 gal pond and have a few fish with ich. I’m unable to catch them. What’s the best way to treat this much volume? I don’t have a heater powerful enough to heat up the water and the weather has been on the cooler side. I have treated with ich x and have added aquarium salt. What else can I do to stop spread and eliminate ich?

    • Hello!
      If you’re unable to catch your fish, then you’re going to have to resort to chemicals. What you’re doing seems to be the best course of action, though the salt might not be as effective with the lower temperatures. I would run the treatment you’re doing for however long is prescribed. Add an air stone or two if possible.
      If you have plants in your pond, just know that the salt might start to affect them.

  2. You mentioned not letting pet store water enter your aquarium. I was wondering how you add your new fish after acclimating them? Won’t some of the water get into the aquarium (quarantine tank) when you release them from their bag/cup/container?


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