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How to Identify, Treat and Prevent freshwater Ich


Ich, better known as ‘white spot disease’ is one of the most common problems which can affect an aquarium. Ich (Ichthyophthirius) is caused by a protozoan parasite called Ichthyophthirius multifiliis. Though the disease is prevalent in all types of fresh water fish, the freshwater fish residing in an aquarium are more prone to suffer from it. This is because ich parasites reproduce in hundreds and the confined spaces of an aquarium aggravates the danger to your fish’s life.

Why does Ich happen?

Ich is a disease with which every aquarium fish has to go through many times in its lifetime. Due to the pervasive nature of this protozoan parasite, most of the fish develop good immunity to fight against it. Ich catches up with the fish when its immunity is compromised. A major reason for lower immunity in fish is stress. And a stressed out fish, with a dipping immunity, is most likely to be attacked by the ich causing parasite.

Some of the causes of stress can be – sudden drop or rise in water temperature, other tank dwellers, water quality, lack of proper shelter, etc. A fish gets the most serious kind of stress when it is transported from one place to another (like from wholesaler to retailer to buyer). That is why many newly acquired fish get affected from the white spot disease.

How to Identify Ich

It is very easy to detect the presence of ich. The fish will develop white spots on the body, fins and gills. The white spots are similar to salt grains in size and colour. You may also notice changes in its behaviour in the form of decreased appetite, irritation, difficulty in breathing, and in attempts to rub against the sides and objects of the tank.


At the advanced stages of the disease, the number of white spots will increase and the fish will continue to get weak and eventually die, if no assistance is extended to it.

There is another ailment quite similar to ich, it is called ‘Freshwater velvet’. Velvet is caused by a protozoan called Piscinoodinium pillularis, and leads to yellowish cysts (which are relatively smaller) on the fish.

Life Cycle of Ich

Ichthyophthirius begins as a free-swimming organism till the time it attaches itself to the body of a fish. The parasitic cells feed on tissue fluids for its growth and are known as trophozoites at this stage of development. Cysts form around the cells; these are white in colour and that is why it has been named as ‘white spot disease’.

Mature trophozoites (known as trophonts) burst out of the wall of the cyst and several tomonts enter the water and settle at the walls, bottom or objects of the aquarium. In a capsule form, each tomont goes through rapid cell division and hundreds of theronts are produced.

When the capsule splits open, numerous theronts come out to look for a host. After attaching itself to a fish the theronts get ready to start the cycle all over again. If they don’t find a host they may not survive for more than 48 hours.

At warmer temperatures, say 75-80 °F, the parasite would reproduce rapidly, and may complete its life cycle even in 3 days. On the other hand, it might take more than 30 days to complete a cycle at lower temperatures, of say 50 °F.

Treatment for Ich

It is very important to treat ich as soon as it is detected, because the ich parasites have the potential to multiply swiftly. The ich parasite can be killed only at the tomont and theront stage of their growth.

You may raise the temperature of the water, preferably to 80 to 82 °F, slowly, over a period of several days. Prior to this, first access how much temperature your fish can comfortably endure. As you raise the temperature, also increase the sources of aeration because at higher temperatures the oxygen gets exhausted faster.

1) Medications

Medicines to treat ich in freshwater aquariums are suitable for most of the standard aquarium fish. And when used as instructed, the medicines won’t harm the aquarium plants or filter bacteria. Before using the medicine, you may consult an expert and/or read the instructions on the medication properly to know if the medicine is safe for your particular breed of fish.

You need to get the entire tank treated for the ich infection. So it is very important to remove activated carbon from the filter as it is likely to remove most of the medication from the water. You can use medicines like formalin, malachite green, methylene blue and copper-based medicines.

2) Salt

Salt is a very effective tool in your hand to eliminate the ich parasite from your water tank. You need to raise the temperature of the aquarium to 82 to 86 °F. Make sure to increase the amount of aeration as well. Salt should be 2/3 teaspoons per gallon of aquarium water. Thus, if you have a 30 gallon aquarium, you need to add 60/90 teaspoons of salt. You should also research about the level of salinity that your particular fish can tolerate.

Don’t put the entire quantity in one go. Take a jug of warm water, add the required amount of salt and put the contents of the jug, little by little, over a period of few hours. This will help the fish get accustomed to the enhanced salinity. It can take about a week for the solution to eliminate ich. Now you can get the water back to normal by undergoing a series of partial water changes; even decrease in salinity need to be brought gradually.

How to Prevent Ich

  • Quarantine

Make it a rule to quarantine all the new fish for at least 2 weeks before putting them in the main tank. You need to observe the fish for about 2 weeks to rule out any possibility of it carrying ich. The quarantine tank can be small but it should have the right kind of environment for the fish to live healthily and happily.

If you buy aquarium plants from a place which used to keep the plant in a fish inhabited water tank then you should quarantine even those plants for at least 4 days. In case the free-living theronts and tomonts came along attached with the plant, they will die in the absence of a fish to attach to.

  • Stress

Stress weakens the immune system and makes the fish vulnerable to attack from various bacteria, virus and other microorganisms. To keep the fish stress-free you need to know the probable reasons which may cause tension to the fish. Some of them have been listed below:

  • Transportation from one place to another
  • Sudden drop in temperature of water
  • High level of ammonia/nitrites
  • Harmony between all tank fish
  • Adequate shelters to hide in the aquarium
  • Water quality

Maintaining high quality of water is very important. Lower the water quality, higher will be the stress and more vulnerable the fish would become to diseases. A decline in water quality is a sure invitation to various microorganisms. Avoid any variations in water temperature, and levels of pH, ammonia and salinity, as these can be very hazardous to the health of the fish. Also, have regular water changes, avoid over-feeding the fish and keep tabs on the chemistry of tank water.

  • Diet

A healthy diet would make a fish healthy and enhance its ability to fight disease. Find out the peculiar nutritional needs of your fish, and give it a mixture of high quality food comprising commercial food as well as freeze dried and frozen ones.

Strengthen your fish by keeping it healthy and happy. And always remember that prevention is always better and simpler than cure.


Shikha Sharma believes that Mother Earth is our mutual abode, where all creatures have an equal right to live with dignity. This belief is clearly reflected in her wonderful writing pieces that revolve around animals and their well-being. She is the blog editor of Pets World.

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