Ick on Goldfish – What are those white spots on my goldfish?

One fine day you noticed your goldfish darting around in the fish tank and rubbing itself against the objects in it. Then you started to see these fine white spots forming on your goldfish as if it was sprinkled with salt little by little. The next thing you know, this “sprinkle of salt” is already covering all of its body.

Well, this is not good.

What you are seeing there is ich or ick on goldfish, and it is one of the most frequently encountered problems in goldfish keeping beside the swim bladder disease. The good news is, ick is easier to treat than swim bladder disease.

Ick On Goldfish
A Ranchu goldfish with ick or ich. There are white spots on its body and fins.

What is ick?

Firstly the term ick and ich are used interchangeably. They both point to the same thing, which is the Ichthyophthirius multifiliis. It is also known as the White Spot disease. Well, whether it is being referred to as ick, ich or White Spot Disease, this is a very common disease affecting freshwater fish and is caused by the protozoan called Ichthyopthirius.



This protozoan is a parasite that lives externally on the host i.e. on the skin, fins and gills of the fish. They will damage the skin, fins and gills as they get into the tissues causing ulceration on the body and breathing difficulties. Open wounds on the body also make the fish susceptible to other parasite or fungal infections.

When a fish tank is already infected, this parasite can attach itself to anything inside the tank, and is easily transferred from one goldfish to another.

Comet Goldfish

What are the signs of ick on goldfish?

Flashing: As the parasite starts to feed on the skin or gill of the goldfish, you will notice that your goldfish darts around the fish tank, and rubbing itself against the objects due to the irritation. This behavior is known as “flashing”.

White Spots: You will also notice white spots which look like small grains of salt, usually start forming on the fins and then on the body. It really looks as if you have sprinkled some salt on it. This is the most telling sign of ick.

Lethargic: Your goldfish will become less active. Its fins will be clamped up and it will often hide or stay stationary in one place.

Gasping for Air: When ick attacks the gills, your goldfish will have problem breathing and you will see it at the surface of the water gasping for air.


How did my goldfish get it?

The Ichthyopthirius parasite can be introduced into your fish tank through the following ways:

1) Addition of new fish
Whenever you add a new fish into your fish tank, you run the risk of introducing “unwanted” things into the tank as well, ick for an example. That is why it is very important to “Isolate First, Socialize Later”. This is also why you should not add in the water from the bag that the new fish comes with.

Goldfish In Bag
Photo by Mark Fischer, CC BY

2) Addition of plants
This parasite does not attack plants. However, it will attach itself to the plants while waiting for the opportunity for a swimming host to come by. So it is also highly recommended to quarantine the plants for 2-3 weeks in a place that doesn’t have any fish. This is because without a live host, this parasite will die off.

3) Addition of decorations
Any decorations including hardscapes may be the hiding place of this parasite if they came from somewhere that is already infected. So always soak them in boiling water before adding them to your tank.




You may think that “OH NO!! My fish tank could already have ick in it” and you are probably right. It is really difficult to be 100% careful on not introducing unwanted stuff into the fish tank.

However, you can breathe a sigh of relief as having ick in the fish tank does not always mean your goldfish will definitely get infected. Goldfish…, well actually all fishes in this matter have this natural immune system that protects them from parasites attacks.

Black Oranda

The problem only comes when your goldfish get stressed. When they get stressed, their immune system gets weaken and exposes them to whatever parasites that are in the tank. This is when infection happens.

Goldfish stress is caused by many factors. The common ones are bad water quality, bad living/shipping conditions and fish bullying (yes, it happens!). Please check out this post on more information about goldfish stress and what you can do about it.

Ick Lifecycle

Well now that you have one goldfish infected by ick, you know that your fish tank is probably filled with this parasite. Although other goldfish in the tank may not show any symptoms of this (yet), it is best to do treatment to the whole tank. With just one fish down, the parasite would have multiplied rapidly.

Before we talk about treatment, let’s take a look at the ick lifecycle. Understanding this will help you know where/when the parasite is most vulnerable for treatment.

Stage 1: Trophont
Trophont stage is also called the feeding stage. This is when the parasite attaches itself to your goldfish’s body, then burrows under the skin and feeds on it. As it feeds, it will also form a cyst. This cyst is the salt-like white spot that you see on the fish.

The feeding and cyst-forming stage will last a few days under the temperature of 24 to 27ºC (75 to 80ºF). Lower temperature will mean that this process will take a longer time to complete. During this process, the parasite is very much protected as it was burrowed under the goldfish’s skin. So any treatment at this juncture will be futile.

When this process is completed, the cyst is now fully formed and it will detach itself from the fish. This cyst is called Tomont or Tomite.

Stage 2: Tomont/Tomite
Tomont stage is also known as the dividing stage. It basically means replication. These free-swimming cysts will look for objects to attach themselves to. Once attached, they replicate within the cyst. It takes another few days to fully replicate and when done, the cyst burst open releasing more of this parasite into the water. The free swimming ick parasite is called Thermont.

Stage 3: Thermonts
Thermonts or swarmers are the free swimming parasite that looks for a new host to feed on. When they find one that’s weak enough for them to attack, they will become Trophont and the cycle continues from Stage 1.



How to treat ick?

So what do we know so far?

  1. Of all these 3 stages in the ick lifecycle, it is only vulnerable to treatment when it is in a free swimming form i.e. in Tomont/Tomite and Thermonts stages.
  2. For it to be in its vulnerable stage, it needs to complete Stage 1. Higher temperature helps this stage to complete faster

Using Salt as the most inexpensive method of treatment

There are many off the shelf medications out there that are targetted for ick treatment, but for this article, we are talking about using the most inexpensive method which is the aquarium salt!

Aquarium salt has been used widely and successfully by fishkeepers for generations in treating this disease. The wonderful thing about using salt is that it will not affect the beneficial bacteria that you already have in the tank.


Okay… so what to do?

Step 1: Raise the Temperature
Raise the tank water temperature slowly to 30ºC (86ºF) so that Stage 1 of the lifecycle can complete faster. Although goldfish are typically coldwater fish, they can withstand a big range of temperature and will do fine in 30ºC. Make sure to increase aeration of the fish tank though to promote gas exchanges.

Step 2: Add Aquarium Salt
Dissolve the aquarium salt with water based on the following concentration: 1 tablespoon of salt for 5 gallons of water, and add it to your fish tank.

Step 3: Do regular water changes & top up salt
Do regular ~25% water change every 2-3 days. Make a note on the volume of water you have removed from the tank.You need to know this in order to know how much salt to top up based on the concentration of 1 tablespoon salt to 5 gallons.

Example: If you have removed 10 gallons of water, you will dissolve 2 tablespoons of salt (because 1 tablespoon to 5 gallons) in the water that you will be topping up to the fish tank.

How long should the treatment be?

Continue the treatment for at least 20 days even when you see your goldfish got better. This is to ensure that you get most (if not all) of the ick parasite out of the way.

All the best in combating ick on goldfish!

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8 Replies to “Ick on Goldfish – What are those white spots on my goldfish?

  1. Hi Alex,

    Great post. My daughter has goldfish so I will send her the link. You really know your goldfish and you have covered this topic really well.

    I had goldfish as a kid and I actually remember seeing something like this on the fish. My dad fixed it but I had no idea this was the problem. Great post, thanks, Kev

  2. This is really great information! I have seen this on our fish before, then before we know it they are all dying 🙁 Now I know that it is treatable for sure. So can you treat the tank even if you don’t see the ick just to keep it away? Like after adding new fish, plants or decorations. I guess more as a precautionary than after it has already infected the fish? Thank you, your website is awesome! I have learned so much!

    1. Hi! Yes, it is always good to be safe than sorry. So we should always take the precaution of quarantining any new fish or plants. As for new decorations, as mentioned it is good to soak them in boiling water to kill of any parasites.

  3. Hi Alex,

    I failed to isolate first socialise later and now all my goldfishs got red spot some with “needle” like on top of the red spot. I tried API melafix as you suggested but doesn’t seems to work. I’m now trying other medication along with salt and heater in hospital tank and it seems to work. My question is, do I need to wipe all of the water in my main tank to completely get rid of the parasite? or can I continue using the same water when I move my fish back to the main tank? Thanks!

    1. Hi,
      I am so sorry to hear about your goldfish but am glad you finally found a remedy. Anyhow from your description, it sounded like anchor worm. In case you are still having this problem, check out this post.

      As for your question, I would sanitize the tank to kill off the parasites, and then add aquarium salt as per the recommended dosage before placing the fish back in.
      Using aquarium salt

      All the best, and do update how it went. Hope your goldfish recover soon!

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