Ichthyophthirius Multifiliis in Fish (symptoms, treatments, and prevention)

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I don’t think there can be any doubt that Ich (Ichthyophthirius Multifiliis) which is often referred to as Whitespot in Europe, is the most prevalent disease in the freshwater fish keeping hobby today.

Left untreated, Ich can and will quickly spread throughout an entire aquarium of fish, proving fatal if suitable treatment is not forthcoming. Ich is treatable and preventable and there are a number of very effective treatments available today.

What is Ich?

Ich, which is often referred to as ‘whitespot’ or ‘white spot disease’ is a disease that attacks both freshwater and saltwater fish, although they are technically two different diseases.

In freshwater fish, Ich is caused by the protozoan parasite Ichthyophthirius multifiliis (which incidentally translates from the Latin to mean “Fish louse with many children”) and in saltwater, Ich is caused by Cryptocaryon irritans.

The speed at which the parasite passes through the various stages of its lifecycle is dictated by the temperature of the aquarium water. The warmer the water, the faster it goes through its lifecycle.

The Ich parasite passes through many stages during its life cycle. The only stage which is visible to the naked eye is the adult (trophont) stage. It is at this stage in the parasite’s life that we see we have the parasite present in our aquariums. Whilst in this stage of the parasite’s life it is immune to treatments.

Prior to becoming an adult, the parasite passes through a juvenile stage known as theront. This is the only stage at which we can effectively treat the parasite. It is because this is the only time the parasite is susceptible to treatments that many people, myself included, recommend treating against Ich multiple times.

When in the trophont stage, the parasite attaches itself to a host fish by burrowing under the fish’s scales. Here, the parasite sits, feeding on the fish until it is ready to drop off and fall to the aquarium floor.

Once the parasite is in the substrate, it sits for a day or two (in the tomont stage) before splitting into hundreds of new parasites (the theront) ready to infect other fish and start the whole cycle again.

Ichthyophthirius multifiliis Parasite

What are the Symptoms of Ich?

  • Small, white spots that usually start on the fish’s tail and fins before spreading across the whole body.
  • Fish may start rubbing themselves against the substrate or decorations
  • Lack of energy
  • Rapid gill movements
  • Scale loss and secondary infection
  • Death

The white spots that give Ich its common name are the most obvious symptom of Ich, however, they are in fact not spots, but rather cysts that form as a result of the parasite burrowing under the fish’s scales.

What Causes Ich?

The cause of Ich in a home aquarium is almost always as a result of new, infected fish being added to the aquarium. It only takes a single parasite to be present on a single fish when they are added to the tank, and within a few days, a large number of fish can be infected.

It is not always possible to look at a fish and see they have Ich (unless they are in the advanced stages when it is usually fairly obvious).

There are other possible ways Ich can enter an aquarium, but they are less common. These include;

  • Using equipment from a tank where the Ich parasite was present
  • Transfering water from a tank infected with Ich
  • Moving plants from a tank infected with Ich
  • Moving filter media from a tank infected with Ich

It is really important to practice good biosecurity when moving equipment, plants, or decorations between tanks. You should be certain the tank you are removing the items from is completely free from ANY pests or diseases.

Ideally, items should be allowed to dry out thoroughly between being used in one tank and another. Alternatively, they should spend a short period in either a bleach solution or a solution containing Methylene Blue.

How To Prevent Ich Entering an Aquarium?

The best way to prevent Ich from entering your aquarium is to quarantine ALL new fish. It doesn’t matter where the fish come from, placing them in a dedicated quarantine tank for 2 to 4 weeks is the best way to prevent Ich from entering your tank.

Strictly speaking, all new plants should also be quarantined, especially if you are concerned snails and other pests may be lurking in the new plants.

To prevent cross-contamination, you should use separate equipment such as nets, water change hoses, and filters in your quarantine tanks. Some diseases can transfer from tank to tank in a single droplet of water.

By placing new plants in quarantine for at least 2 weeks, the life cycle of the majority of pests and diseases will be broken, providing there are no fish in the quarantine tank.

How to Treat Ich?

Ich is a disease that is 100% treatable, providing treatment begins early. If Ich is left to overrun an individual fish, it can prove fatal.

There are dozens of different medications on the market to treat Ich. In my experience, the most reliable treatment for Ich has been Ich-X which is made by Hikari (check the current price of Ich-X on Amazon.com).

There are many articles online that suggest you can treat Ich by raising the temperature of the aquarium water. This is partially true. By increasing the temperature, you speed up the Ich parasite’s lifecycle. The faster the lifecycle, the easier it is to treat the Ich when it is in the free-floating stage of its lifecycle.

However, bear in mind, increasing the temperature beyond the fish’s normal temperature range may cause the fish stress, or even prove fatal.

Further Information

Ich, like so many diseases, takes advantage of fish that are stressed, or otherwise have their immune system compromised.

To ensure your fish have the best chance of fighting off any diseases, make sure their water is of the highest quality by carrying our regular water changes.

Also, feed your fish a varied diet made up of good quality foods. The better a fish’s diet, the stronger and healthier it will be.

About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James