If your fish have white spots on their body, they may have got “Ich,” the white spot disease caused by the parasite Ichthyophthirius. Ich is a common parasitic infection of freshwater fish and is one of the few diseases seen with the naked eye.

While white spot disease is widespread in freshwater fish, it seems more prevalent in aquarium fish. This problem may be due to the closer contact and stress involved with aquarium species.

Since Ich is a highly contagious disease, you need to understand what causes your fish to fall ill. Read this article to understand the causes of white spot disease and ways to reduce the risk of Ich outbreaks in your tank.

How to Know if Your Fish Have Ich

When fish get Ich, they have tiny white spots on their bodies, like someone sprinkled salt or sugar on them. Ich is more noticeable on the fins first since there’s less slime coating them, making it easier for the parasite to target.

One way to be sure if your fish has white spot disease is that there are five spots one day and then maybe 30 white dots the next day since Ich multiplies rapidly.

However, some fish get stress spots or “stress ich,” which evenly covers the entire body, not just the fins. If you see five white dots one day and they don’t increase, it may be anxiety which causes your fish to develop these symptoms.

A fracture to the cartilage of a fin can look very similar to white spot disease. Breeding tubercles on male goldfish may also lead to multiple white bumps on the pectoral and operculum fin. Lymphocystis, a viral infection in fish, can produce similar white bubbles.

– Symptoms of White Spot

The symptoms of white spot disease are apparent. It begins with the characteristic white spots on the body and gills. However, in some cases, you will only find the ich parasite on the gills.

As the infection progresses, the fish will try to rub or scratch against the sides and bottom of the tank to stop the itching. You will notice signs of respiratory distress as the fish begins to breathe rapidly.

Soon your fish will lose their appetite. Their eyes become cloudy, and they start to hide. It also takes them very long to swim to the top of the tank. The fish can become more susceptible to bacterial infection.

What Are the Causes of White Spot Disease?

Parasites are naturally present in tanks, but the immune system of healthy fish can easily overcome them.

The Ich parasite can either be introduced into your tank by new inhabitants or dormant in the aquarium. Fish with a robust immune system can maintain a balanced parasite-host relationship for a long time. The parasite cannot infect healthy fish, making it difficult for the parasite to reproduce, keeping their population under control.

New arrivals to the tank are ideal victims of parasitic infection. They may have a weak immune system caused by the stress of transportation and being introduced to a new environment. Hence, they are highly susceptible to the parasite.

Suppose you see the unexpected appearance of Ich without new arrivals in the aquarium. In that case, the reason could be the water parameters or a crowded tank that weaken the fish’s immune system.

Some additional factors that may lead to white spot disease are:

  • Failure to quarantine new fish
  • Excess waste in the tank
  • Toxic levels of ammonia and nitrates
  • Fluctuating pH
  • Insufficient dissolved oxygen content
  • Infected equipment
  • Untreated Decor
  • Lack of good hygiene and maintenance

Understanding the Life Cycle of the Parasite

The life cycle of the Ichthyophthirius multifiliis parasite consists of three stages. The trophont burrows under the skin of the fish, where they feed and grow. The fish coats the parasite with a layer of mucus to protect themselves. At this point, the spots will be big enough, and you will see them on your fish. You cannot treat white spot disease during this stage because medications cannot penetrate the cyst.

Once the blister bursts, the trophont settles at the bottom of the tank and secretes a thick, gelatinous coating to form a cyst. It then divides into hundreds of new tomites, which are released and swims off, searching for a fresh fish host.

Tomites have to find a host fish to attach themselves to within two days, or they will die off. The complete parasitic life cycle is temperature-dependent. At higher temperatures, the parasite reproduces faster. In comparison, lower temperatures will slow down the process and give you more time to eradicate them.

The tomite stage is the only time the parasite is susceptible, and you can treat it with medication. This limited time frame makes it crucial to repeat the treatment to ensure that you have destroyed all the parasites. Failure to complete the treatment usually leads to a new outbreak since one parasite can produce hundreds of new ones.

Treatment of White Spot Disease

Since you can only kill the ich parasite in the tomite stage and their life cycle is temperature-dependent, you need to raise the tank temperature to 78 – 80 F to accelerate the tomite formation and release.

If their life cycle is complete in four days, it gives you four days to complete the treatment. On the other hand, if you keep the temperature at 60 F, you must carry out the treatment for several weeks.

Since you cannot kill Ich while it is in the fish, moving a fish to a quarantine tank for treatment will not solve the problem in the main aquarium. If one fish in a tank gets the white spot disease, you must accept that the entire community of fish is now infected, and you must treat the whole tank.

Another way to eradicate Ich from a tank is to remove all of the fish. Tomites can only survive without a host fish for two days. So if you transfer all of the fish into another tank and then increase the temperature to 80 F, the parasite in the tank should die after two days. To be safe on the safe side, give it a couple more days before returning the fish to the tank.

It is essential to remember that you will need to treat the tank before you move the fish. Otherwise, fish entering that tank could become infected. You have to treat the tank since you cannot treat the fish. As a result, all treatments are designed to kill the parasite in the trophite form while in the tank.

Some of the best treatments for white spot disease are malachite green or formalin, or even combining both. It is best to use freshly purchased formalin since formalin that has been stored for a long time can convert to paraformaldehyde, which is dangerous to fish. If you see a white residue in the bottle, it is unsafe to use it.

If given at the recommended dose, malachite green may be harmful to neons, sunfish, piranhas, neons, and some scaleless fish. We suggest that for these fish or other sensitive species, you should treat them at half strength and monitor your fish closely for any signs of distress.

It is best to follow directions on the label. You will also need to remove the carbon from your filter and turn off any UV sterilizers during treatment.

– Preventing White Spot Disease

White spot is a prevalent disease in ornamental aquarium fish. Unfortunately, if your fish gets infected, you are going to end up treating the entire tank. Therefore, it is wiser to take precautions to prevent this disease rather than to treat it.

Here is a list of suggestions we hope will help you to prevent your tank from getting infected:

  • Always keep new fish in a proper quarantine tank for at least two weeks before you introduce them into your tank.
  • Never buy plants from a shop that keeps them in a fish tank with fish. If you do, make sure to quarantine your plants for at least four days.
  • Remove any fish that displays symptoms to a quarantine tank right away to begin treatment.
  • Monitor your water parameters regularly as fluctuations are very stressful to fish and can cause an outbreak of Ich.
  • Give your fish a balanced diet for a healthy immune system.
  • Do not overstock your tank. Too many fish and lack of space result in disease and stress.
  • Perform routine maintenance tasks and carry out regular water changes.


While Ich may be the most common disease in aquarium fish, it does not have to infect your tank. Here is a summary of some facts:

  • Spend some time every week to check your fish to detect early signs of disease.
  • White spot disease is highly contagious.
  • The parasite cannot be killed when it is in the fish.
  • Once the parasite grows, it looks like salt sprinkled on the fish.
  • It would be best if you carry out the treatment for the entire tank.

By following these preventive guidelines and promptly treating any infected fish, you can significantly reduce the damage caused by this deadly disease.

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