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Treat Ich in your Freshwater Aquarium – Fast and Effective

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Ich, also known as “whitespot disease” or “ick”, is the most common diseases known to the aquarium hobby. Because it is so widespread, everyone that keeps fish will encounter the disease at some point. And, as you are reading this article, chances are that you have to deal with this disease right now. The article will contain a lot of information on first understanding the disease, then teaching you different ways to cure it and finally how to prevent getting ich in the future.

What is Ich

Clown loaches with ich, notice how difficult it can be to see

Ich (Ichthyophthirius multifiliis) is a parasite infection. Believe it or not, ich is present in almost any aquarium. Especially in the fish tanks of stores and wholesalers, as they handle a lot of different fish from different locations.

But why don’t all fish suffer from ich than? Well, because they have built an immune system. As soon as the fish’s immune systems weakens because of stress or other reasons, they are vulnerable to an outbreak of ich.

There are numerous things that you need to understand about ich to know how to effectively cure it. You will first need to know all the symptoms of the disease, so you can recognize ich in your tank. After that you need to get a basic understanding of the life cycle of the disease, so you know at what point the disease is susceptible for treatment. Let’s first start with the symptoms.


At the infant stage of the disease, there are hardly any symptoms. When the parasite is introduced to your fish tank, it will find a fish to nest on, and it takes a short while before the fish will show any symptoms. This is because the parasite yet has to start feeding on the fish, and with this a white spot will occur and grow. This is the first and foremost symptom that you have ich in your aquarium. Below is a list with more probable symptoms of the disease.

  • White spots – The most common symptom that people notice are the white spots on the skin of their infected fish. They can be up to 1,5 mm (3/64 inch) big and look like grains of salt stuck to the gills, skin and fins of the fish. These spots are tiny cysts and mark the spots where the parasites have nested.
  • Scratching – The white spots irritate, which makes the fish rub them on rocks and ornaments. This is called flashing, and is something your fish already do without ich. With the disease, look for excessive flashing.
  • Rapid breathing – The parasites nest in the gills of the fish, which hinders the oxygen intake to their blood. This might cause them to breath rapidly and gasp for air at the surface.
  • Anorexia – The fish will refuse food and you will not see it eat in general. This is a result of too much stress because of the infection.
  • Cloudy eyes – This is a symptom of ich, but this disease is not the only potential cause. It can also be caused by other factors such as old age, stress or poor water quality. Just this symptom requires further investigation.

Life Cycle

The life cycle of the Ichthyophthirius multifiliis, the parasite that kills our fish, is important to understand. The parasite is an ectoparasite protozoan, which means that it is a single-celled organism that lives on the surface of the host (our fish). This is the first stage, and the first chance you will be able to see some symptoms. Right now the organism is called an ich trophont.

  • Trophont has penetrated the skin and lives in the skin of the fish. During this stage the disease can not be treated, because the fish capsules of the parasite in order to reduce damage.

When the trophont has fed enough, it leaves the fish. It will fall down on the ground and develops into a tomont. When the disease is in tomont stage it is encapsulated and this stage is also called the dividing stage. It will stick to plants, gravel, wood and other ornaments in the tank. It will divide into so called theronts.

  • Trophont falls down and becomes a tomont. It will stick to objects in the tank and while encapsulated will start dividing into thousands of dangerous theronts.

The encapsulated tomont will sit in your aquarium and divide into dangerous theronts, where one tomont can become over a thousand theronts! This brings the disease to the next stage, where the tomont will burst opens and release all the theronts into your aquarium! Now that these parasites are set free, this will swim in your aquarium freely looking for fish to house on. It is at this stage that the disease is vulnerable for treatment! Now is the time to strike, because the theronts can be killed before they find a new fish to nest in.

  • Encapsulated Tomont bursts open and release a lot of dangerous theronts into your tank. These theronts will swim around freely to look for new hosts. It is at this stage that ick is vulnarable for treatment.

Important: Because Ich is a parasite that breeds in the water, you are not curing your fish but you are curing your tank. If you only remove the fish from the aquarium, the disease is still in your tank. Therefore, cure the whole tank.

Treating Ich

  • Speed up the parasite’s life cycle by increasing the heat if possible
  • Medicate your tank with medicine
  • Make sure to remove all active carbon from your filter as this removes the medicine
  • Watch for other infections because the fish’s skin is damaged
  • Another treatment is to empty your tank for 4 days and treat the fish in a small container

The life cycle of ich makes treating this disease difficult, because the parasites are encapsulated most of the time. It is only vulnerable during a limited time window, when the trophont has burst and all the theronts are floating freely through your tank looking for a new prey.

Raising water temperature

Because the duration of the life cycle is so temperature dependent, the first step to treating the disease is raising your fish tank’s water temperature to about 27 – 28 °C (80 – 82 °F) . This will speed up the cycle and push the parasite to its vulnerable state quicker.

Note that raising temperature is only possible if your fish allow it. If you have cold water fish (like koi or goldfish) you can not raise your water temperature to 28 °C (80 °F). So make sure you research your fish! If it is possible, raise your aquarium water to shorten the cycle. If not, ich might not kill your fish, but you will by raising the temperature.

Medicate your tank

Together with increasing your water temperature you should medicate your water to kill the parasites when they are looking for a new fish to bury into.

Important: Remove all active carbon from your filter as it will remove the medicines.

To medicate your tank, there are a lot of different brands of medicine available on the market. Most of them contain formalin or malachite green, or a combination of those two. Other chemicals like methylene blue, mepachrine hydrochloride and quinine hydrochloride are also effective. Again, these are available in many places under many different names.

One medication which will definitely help you is called Ich-X and is super popular in the hobby. You can easily get in on Amazon here, and it will solve your ich problem!

Using salt to treat Ich

A lot of people use salt to cure ich, as it can be a very effective treatment. However, you have to be careful to not use it of sensitive fish like loaches, puffers and catfish. Salt can be a very good treatment for fish like cichlids and goldfish.

Empty your tank for 4 days

If the theronts (the free flowing parasites looking to dig into new fish) are not able to find any new prey, they die. This happens after around 48 hours when the water temperature is 27 C (80 F). So if you are able to remove all the fish from your aquarium, it is a possibility to treat your fish in a way smaller container and let all the ich that is in your main tank die off. This is a good idea when your tank is too large to easily treat with medicines, or when you only have a couple of fish in your tank.

You can house your fish temporary in smaller tank, make sure to add a small heater and an air stone to ensure perfect water quality. The air stone increases surface agitation, and it is important because in warmer waters the water can hold less oxygen.

Watch for other infections

Because of the ich, the immune system of the fish drops. Next to that, the places where the ich has entered the skin or gills of the fish will become small wounds. If the fish is weak these small wounds are very sensitive to extra infections. Keep this in mind and watch your fish closely.

Preventing Ich

  • Quarantine your new fish for 4 weeks and watch for signs of ich
  • Watch out for fish that already show symptoms of ich in the store
  • Know that stress reduces the fish’s immune system and might cause ich

With ich, it is way easier to prevent the disease that to cure an entire tank at once. This is why quarantining your fish is so important. Whenever you buy new fish, put them in a separate tank for about 4 weeks. If the fish is stressed because of the buying process (shipped from wholesaler to fish store etc) the ich might kick in. The quarantine processes allows you to notice this and treat the fish accordingly.

Even better is to avoid buying fish that have ich in the first place. Because we already established that almost all fish tanks contain the virus (especially in fish stores), we should primarily watch out for fish that already show symptoms. If you do not see any symptoms you can just stick to the regular quarantine process.

Finally, keep in mind that stress is the reason that the fish’s immune system will reduce. When this is the case, the fish are susceptible to ich.

To conclude

With ich, preventing is way more important than curing. And also not that difficult if you quarantine your fish. If you do get ich, know that it is a parasite that lives in your tank. Therefore, you can not cure just the fish, but you have to treat your entire tank.

I hope this article helped you a lot when it comes to the disease “ich”, and that you can use this information to successfully cure your fish.

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