You probably bought some fish from the pet store because you enjoy watching them. You don’t intend to breed or sell your fish, nor do you plan on having anything terribly fancy. Keeping fish is easy, right? But lately you may have noticed that your fish have started to swim erratically. Then they developed white spots on their bodies. Soon you start panicking because many of your fish have begun to die! Your fish most likely have “Ich”.

Ich is short for Ichthyophthirius multifiliis- you can understand why nobody wants to pronounce the whole name! Ich is the most common disease of aquarium fish. It is an infectious and contagious disease. This means that one of the fish you bought was infected with Ich and spread it to the rest of the fish in the aquarium.

Ich is a type of parasite called ‘protozoa’. This is a very basic organism that divides by binary fission (splits in half). To simplify things, Ich has three stages in its life cycle. The first stage is when the organism invades the skin of the fish. This is the stage where the damage occurs to the fish. The organism eats and destroys red blood cells and skin. It then leaves the skin, sinks to the bottom of the aquarium, and forms a structure called a ‘cyst’.

In the second stage of the life cycle, the organism divides (by binary fission) within the cyst, forming thousands of new protozoa. In the third and final stage, the cyst breaks open and all of the newly formed protozoa invade the skin of a fish. And so the cycle continues.

As mentioned above, the white spots are caused by the first stage, when the parasites are living in the fishes’ skin. This obviously causes direct damage. Damage to the skin is always bad news to the fish. The skin and the mucous layer on top of the skin are a fish’s key defense mechanisms. Once the skin is damaged, the fish has less control of the salt and water balance inside of its body and is also more prone to bacterial infections. These problems can quickly become fatal to a fish.

The treatment for Ich is to treat the water in the aquarium. The chemicals of choice are either formalin or copper sulfate. You will need to treat the tank more than once, because Ich cannot be killed when it is in the skin or in the cyst stages. With multiple treatments you will be able to kill Ich as it changes through the life stages. The size of the tank and the temperature of the water determine the amount of chemical you need to use and how often you need to use it. Your local pet store will be very familiar with this disease, and will be able to help you decide the right treatment regime for your tank.

Ideally, the best thing you can do is to avoid having Ich in the first place. This is done by quarantining new fish before you introduce them to the tank. As we mentioned before, Ich is contagious, so the only way your fish can get Ich is if you buy a fish with Ich. What we mean by ‘quarantine’ is separation of new fish in a separate aquarium (or bowl) for a certain amount of time. This way, if you bought a fish that has Ich but doesn’t have white spots yet, there will be enough time for the disease to show up before you put it in the tank with all of the healthy fish.

Ich is a very common disease in household aquariums. It is caused by a small parasite that invades the skin cells of fish. The best way to prevent Ich is by quarantining all new fish. In fact, quarantine is a good way to prevent many other diseases from spreading into your aquarium. Before you decide to treat your aquarium for Ich or set up a quarantine tank, make sure you talk to someone who sells fish, or your veterinarian, about what will work best for you and your fish.

By Ashley O’ Driscoll – Pets.ca writer