Ichthyophthirius multifiliis (or in a more shorter term ich or ick) is a very common disease that effects both freshwater aquariums and ponds. Ichthyophthirius multifiliis is a disease that is caused by the protozoan Ichthyopthirius which is commonly noted for leaving the fish who are infected with small white specks that appear to look like salt on their body and gills. If left untreated or by giving the wrong treatment to any fish that may have this disease, can lead to the death of not only the infected fish but also any other inhabitants that shared the same water.


Ich is very common in the aquariums due to the fact of how the fish are stressed when transported from the breeder's to the aquarium store, and finally to your own aquarium or pond setup. In reality, every fish will come into contact with this protozoan multiple times throughout it's life, however in most cases the fish has a good immune system which allows it to fight off the protozoan before any infection occurs. The symptoms of ich are very evident as there will be small white specks that appear to look like salt on their body, near and also inside of their gills. As the disease progresses the fish might start to try to rub against decorations, the substrate, and any aquarium or pond equipment that is inside of the fish's location. This disease can cause the fish to become lethargic, breathe heavily and rapidly (when swimming or near the top of the water's surface), and lastly it can cause death.


In order to understand how to treat ich completely, we must first understand how ich lives and reproduces. In order for this to make better sense, we'll start off when the ich protozoan attaches itself to be fish's skin and starts to cause some irritation. The fish will start to react by trying to block off the protozoan from getting into it's blood stream where it would do more damage, and therefore protecting itself and it's vital organs. The ich protozoan will then start to build a cyst on the fish's skin feeding and growing bigger and bigger, which in this stage the protozoan is now called a trophozoite. The trophozoite will later mature enough to turn into a trophont, where it will burst through the cyst wall and be carried by the aquarium's water column. This in tern then releases multiple tomites, which is where the ich is reliant on the temperature for the tomites to develop so that they can be released into the water column where they will repeat this process over and over.

In colder temperatures it can take anywhere from days to weeks for the tomites to be released into the water column, however warm temperature will speed this process up anywhere from days into hours. The stage in which ich cannot be treated is when it has already formed a cyst wall on the fish's tissue, as no medicine can penetrate the cyst making the trophozoite unharmed and still able to develop and grow. However, there is a stage in which ich is the weakest and is where it can be killed at very easily. When the tomites are released into the water column, they are very weak and known to only live up to a day without a living host. They can attach themselves however to plants, filter media, decorations, or even components such as heaters, filter intakes and outputs, the walls of the tank, and more. Since they can attach themselves to almost anything within an infected setup it is recommended to never remove, add, or change any components or inhabitants within the setup until the treatment is finished and fish show no signs of ich.

Treatment and Medication

Since we now understand the life cycle of ich, we can see that our treatment has some guidelines that it must follow in order to kill ich at it's weakest point. This is why various treatments should make more sense, and why many suggest raising the temperature in order to help speed up the life cycle of ich in order to kill it. As we cannot kill ich while it is on the fish, we need to remember that removing any fish during this period (if showing signs of being infected or not) can lead to the new tank becoming infected with ich as well.

One of the most recommended methods to killing ich is to raise the temperature up to 80-84 degrees Fahrenheit (26.67-28.89 degrees Celsius) over a period of days in order to not shock any inhabitants. By leaving the temperature this high, we are speeding up the life cycle of ich while also killing off any tomites that have been released or are attached to components in the water.

Another method that is highly recommended when treating for ich is to use formalin, malachite green, or a mixture of both of them combined. When using any medicine, it is recommended to remove any carbon from the filter media and to also turn off any UV sterilizers or protein skimmers during usage. It is recommended to remove all decorations in the tank before using malachite green as it can stain them a slight shade of green throughout the treatment and if you have any sensitive species within your aquarium please use these medicines at roughly half strength. We recommend following the product's instructions on the bottle when using either of these products.


Due to the way that this disease spreads and effects the inhabitants, the best prevention methods are to always make sure that you quarantine anything that you place inside of your water (this includes any plants, inhabitants, decorations, and more). Thus, when you do let them adjust to your water and you truly see how they are acting, eating and if they have any symptoms or signs, we will either start to get a better understanding if they are infected, or learn about what possible other diseases they might have.