Best way to treat white spot fish disease in reef tank

Best way to treat white spot fish disease in reef tank reefpedia

Marine white spot disease is one of the most common marine fish diseases noted by fish keepers in saltwater aquariums. Do you know how to treat white spot disease in fish tank? Can you save aquarium fish with white spot? How long does it take to treat white spot in fish? Read the article and find all answers.


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What is white spot disease in fish tank

Cryptocaryon irritans infection is a bacterial infection known as a white spot disease caused by protozoan parasite. This disease is known as “marine ich”, “Saltwater fish Ick” disease.

Cryptocaryon is a filamentous protozoan and it is present in saltwater environments. The protozoan penetrates the fish’s skin and gills of marine fish species. Depending on the immune status of the infected fish, it can cause mild symptoms like a few small white spots to more serious problems like loss of appetite, weakness, severe respiratory distress and even fish deaths.

Why do fish get infected with white spots fish disease?

In nature, there is a low probability of the fish getting infected with ich parasite and becoming seriously ill. Though in saltwater aquariums, due to the fact that the volume of aquarium water is quite small, Cryptocaryon irritans infections can develop quickly and effectively.

In addition to the above, the reasons why fish can get white spots disease are:

  • increased levels of stress, caused by environmental factors (water temperature),
  • aggressive behaviors of other saltwater aquarium fish species,
  • and poor diet.

These factors reduce the naturally present healthy immune system of a healthy fish and make the protozoan’s task easier.

Which fish are more likely to get white spot disease?

Some fish which are more sensitive to stress and various environmental aspects can be much more susceptible to Cryptocaryon irritans infection. These are fish species more vulnerable to the white spots infection:

  1. Beard fishes (fishes with beard)
  2. Achilles tang fishes
  3. Paracanthurus hepatus known as a blue tang can also get saltwater ick disease due to its susceptibility to stress.

What are symptoms of white spots disease in fish

White spot fish disease is quite easy to be recognized due to the characteristic white spots appearing on the infected fish. At first, there are only a few of them, but if the fish is weakened, you will quickly notice many more white spots.

As the disease progresses, sick fish can have problems with eyes. You may notice that the fish’s naked eye becomes cloudy. Secondary infections may occur over time, ich life cycle lasts three weeks.

How to treat ich in saltwater tanks

Can white spot disease be cured? Yes, it’s possible. How to kill ich infection? Firstly, it’s very important to detect the ich infection at an early stage. To begin with treating ich, we should remove the cause of stress or whatever is causing the problem in reef aquarium.

The treatment may possibly last for five days to one week. It depends on the time you need to remove the fish parasites from the infected fish.

Infected fish should be bathed in RO water (reverse osmosis, temperature the same as aquarium temperature) – after a while in boiled RO water. As a result the protozoan will fall off the fish’s body. Remember that the water must have the same temperature as the water in the aquarium and a similar pH.

Sometimes reef aquarists recommend making baths in preparations with copper. But be careful with such baths because some saltwater fishes, such as Zebrasomas (surgeonfishes), are very sensitive to copper.

Will salt cure white spots? Aquarium salt definitely can help. Use 1 Tbsp sprinkled salt per 2 gallons of water for a period of 10 days.

There are also safe formulations on the market that can be used in the main reef tank, such as PolypLab Medic. PolypLab Medic is a very effective antiparasitic water conditioner which de-pollutes water. It is used in both marine and freshwater aquariums to improve water quality.

During the fight against the parasitic infection, it is worth turning on a properly selected UV sterilizer, which will allow us to knock the pest out of the entire tank water.

How to prevent the white spots disease

White spots disease is easily preventable. Surely, treating infected fish is much more difficult than preventing them from getting sick. Here are the best tips for white spot disease prevention (ich prevention):

  • Always buy new fish from a trusted fish store – the cheapest fish will not always be the best choice. It’s worth paying extra to be sure that we decide on a fish that is in a great condition and have healthy immune system,
  • Choose the right fish for your reef tank (consider quantity, tank readiness and aquarium maturation level, animal aggressive behaviours, and your marine experience),
  • Especially make sure to feed the new fish properly, which will allow them to acclimate easier and quicker,
  • Monitor fish health and react in advance.


As described in the article, there are several effective ways to get rid of white spots fish disease and prevent ich in a reef tank. Of course, if you buy a sensitive fish for which the tank is not ready yet, you can face a disaster. On the other hand, if you will remember to get a quarantine period and quarantine tank, and the white spots disease will be noticed at the early stage, you will solve this problem much easier and faster.

Want to find out more about marine fish and saltwater aquariums? Read other helpful articles written by aquarists experts on the blog here!

About the author

Picture of Marek Protasewicz

Marek Protasewicz

Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.

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