Goldfish Lice – How to Treat Them, Spot Them, and Prevent Them!

To look after our goldfish to the best of our ability, it is fundamental to know how to handle them best. We want to understand everything that could go wrong in our fish tanks, so we are prepared to act if anything unfortunate was to occur.

Like with most fish, you may be worried about your goldfish harboring any excess parasites – a common concern that fish are notorious for.

One commonly occurring problem in goldfish is lice – something which we will go on to talk about in further detail within this article, to educate ourselves in how better to prevent or treat our pets from this persistent problem.

What are Goldfish Lice?

When we say lice, you may automatically think of woodlice, or lice that you used to get in your hair when you were younger – but this is not the case.

Goldfish lice are actually a type of crustacean whose Latin name is Argulus trilineatus. These particular lice can be found infecting your goldfish – although, to the naked eye, they may only look like small specks of dirt. Despite this, goldfish lice can grow up to 3-5 millimeters in length, with a flat circular shell with 8 legs, and often appear translucent.

Lice will attach themselves to your goldfish with their small hooks, leaving room for further exposure of the goldfish to bacteria once they have finished eating. We know that lice cannot survive long on one particular goldfish, so in time they will move on to affect others within the tank.

Typically, lice tend to be more of an issue within outdoor ponds. However, that is not to say they cannot affect fish tanks; it is just that the statistics suggest higher infection rates within pond-life. For this reason, you will need to be careful where you buy your fish, making sure they have come from a healthy background.

The other problem is that lice prefer freshwater fish, so our usual procedures of dealing with sickness won’t’ work. Usually, we suggest doing tank checks, making sure everything is clean, at the correct temperature and pH level – however, this will not help to eradicate the lice.

What Causes Lice in Goldfish?

There are several reasons that your goldfish may deal with an infestation of lice.

If your goldfish is turning black, however, it can be a symptom of something else entirely. Read about it here! The number one reason that this happens is due to not quarantining them before introducing them into your main tank.

Goldfish are so susceptible to different parasites, so without quarantining them properly first, you are basically moving bacteria and parasites around with them whilst infecting your tank.

Lice are easily transferred from fish that may have had contact with other wild fish or plant life. Lice, like other types of parasites, will live on a particular host until it finds a new one, although it is not only fish that can transfer lice but actually anything that has had contact with previously infected waters – for example, plants or even aquarium ornaments. For this reason, we must make sure that anything we are putting into our own tanks is clean!

What are the Symptoms of Lice in Goldfish?

Now that we understand the potential causes of lice on our goldfish, we must be able to identify the symptoms as quickly as possible – so we can get rid of them and protect the rest of our tank.

The symptoms include:

  • Your goldfish may be more lethargic than normal
  • You may notice that they are rubbing themselves on the tank, or on rough surface areas to scratch their itch!
  • They may appear stressed, which can mean they are overly energetic
  • You may notice little dots on your goldfish, which at closer inspection you may notice look like little tiny crabs!
  • Scale loss or torn fins
  • Discolouration

While some of these symptoms are similar to other illnesses that goldfish are susceptible to, identifying lice on the goldfish’s body will give it away. You may find lice in the more sensitive areas of your goldfish, particularly in their eyes, gills, or fins – so it is important to be vigilant with these particular pests!

If we do unfortunately find out that we’ve’ encountered lice within our fish tanks, ideally, we need to know the best ways of treating them!

How do you Treat Lice in Goldfish?

When we are treating the lice, we know that they will drop off the host goldfish after two hours. Once this happens, we need to remove our goldfish from the main tank and put/them into a secondary tank for treatment.

Once in the secondary (or hospital) tank, we are able to identify the ways in which we want to treat our goldfish for lice. One way of doing so is with the use of non-iodized salt. This is the best and most natural treatment for your goldfish, where you make sure that the second tank has all the same temperature and pH level checks, and then begin the process by adding two teaspoons of salt per gallon.

Although this is a natural remedy, your goldfish may become a little stressed as they are obviously freshwater fish; however, we will only need them to settle in the salt for around 3 to 4 days. After this time, you should begin to notice that your goldfish are no longer covered in lice. You should also see that they have no new tears or scale loss, and they should’ve stopped the itching behaviors around the tank.

If you do not see any changes within your secondary tank and you feel as though the lice are still affecting your goldfish, then you may need to use a different treatment. If you do decide to use a different treatment, we recommend an insecticide that you can buy from most aquatic stores.

When purchasing insecticides, it is important to remember that this will also affect the water quality that your goldfish are in. When buying this treatment, we advise that you do, please check with the aquatic experts at the store so as to cause as little disruption as possible, with the most effectiveness – as we understand that the goldfish’s wellbeing is the primary cause for concern when dealing with harsher treatments.

Now that we have treated our goldfish, we need to treat our tank in which the initial infestation had occurred. We can do this by boiling any ornaments in the tank first, ensuring that they are clean and safe before we put them put back in. By boiling them, we kill the lice; however, this should also be done initially when you first purchase any new ornaments to put in your tank. Although, sometimes, despite our best efforts, the infestation has been put in after.

Next, we need to clean our plants thoroughly, making sure we have removed any specks of dirt that may be potential lice or larvae. You may want to consider beginning again with your plant life; however, that is entirely up to you as it can often be expensive – so once you have cleaned them properly, they should be fine!

We also want to ensure that we have drained the tank, cleaned, and hoover the substrate. If you have a sand-like substrate, then the lice may be easier to see. However, with rocks that are similar sizes, they may get missed. Again, you may find that you want to buy a new substrate, and this is not necessary with a thorough cleaning.

Please ensure that once you have thoroughly cleaned your fish tank and feel ready to place the goldfish back in after treatment, your tank is in the optimal environment for your goldfish.

If the lice have affected your goldfish in any way, then they will have lower immune systems than before, which means they run a higher risk of picking up other illnesses. Please ensure that the tank is at the right temperature and pH level, so your goldfish do not get more stressed and go into shock after being placed back in.

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How do you Prevent Lice in Goldfish?

We recommend the same advice whenever you are acquiring a new fish, which is to quarantine them! We want to quarantine our new goldfish for around two weeks, as in that time, we can gauge any potential issues that they may have brought with them from their original tank.

You may ask the person you buy your fish from whether they have been exposed to or treated for any previous parasites or infections, but you cannot be sure that it has definitely been identified, hence why the period of quarantine is important.

Along with all fish, goldfish are known to carry parasites and bacteria, so it is how you first interact with them that will be fundamental in determining what happens with the rest of your tank.

We want to ensure that when we quarantine our new goldfish, the environment is to the best of our abilities so that we do not have any unnecessary stress, which could make any impending illness worse.

We need to make sure that our quarantining tank has the right pH level, ideally being between 7.2 – 7.8 for goldfish, with the temperature staying between 20-23 degrees celsius. It is also extremely important that you do not transfer the water from the aquatic store tanks, where you purchased your fish, to your personal tanks. This will again decrease the chances of infestation, as again, we do not know exactly what is hiding in the previous tank!

Are Lice in Goldfish Contagious?

Unfortunately, goldfish lice (like most other lice) are extremely contagious, which is why we want to treat the problem as soon as we find it! They are detrimental to your goldfish’s health due to the fact that they use them as food sources and gnaw away at them during their occupation!

Lice typically feed on one host for around two hours before unlatching themself and finding a new host in the tank. Before you know it, if you have a community tank, and all your goldfish have become stressed and injured.

Stressed goldfish are going to move around the tank more and rub themselves on objects that your other fish will come into contact with, so just like our own viruses and bacterial infections, it spreads quickly.

Is Lice in Goldfish Fatal?

If left untreated, then lice infestation in goldfish can be fatal. This is due to the feeding nature of the lice more than anything. Once the lice latch on to your goldfish, they will begin to feed on your fish’s tissues.

Lice will usually stay on the goldfish for around two hours before dropping off and finding a new host to feed on while also multiplying. Although it is not the lice themselves that actively kill your fish, but more so the damage that the lice have done.

Leaving the lice untreated in the tank will mean the goldfish will be repeatedly latched on to by the multiplying lice, creating lesions and even open wounds in your goldfish’s body, weakening it. These lesions will mean that your goldfish is at greater risk and more susceptible to bacterial infections, leading to fatalities within your fish tank.

The other worrying aspect of lice is that they may also harbor other diseases, parasites, and bacteria that may be transferred to your goldfish when feeding.


In conclusion, we understand that a lice infestation of your fish tank is expectedly very annoying. You need to be fast-acting when it comes to lice, as they want to live off of different fish rather than just one. This means that when you identify the problem, it can get quickly out of hand.

We always recommend natural remedies with regards to treatment for our goldfish, as it is the kindest and least invasive to our tank environments. However, we do understand that sometimes this option is not viable.

The key to so many health problems for your goldfish consists of how you first deal with it. When you buy your goldfish, you must quarantine it for the first two weeks, so you can deal with any issues before infecting the rest of your tank. We know that prevention is the most important part of dealing with illness, and quarantining your fish helps this.

Always ensure that you get your goldfish from a reputable place, so you know that the fish has come from good, clean environments, but do not take any risks with your goldfish’s health.

About the author

Hey! I'm Antonio!

Betta fish keeper for over 6 years now! Since owning a betta I've also housed all kinds of tropical fish, and have seen all manner of problems and how to look after them!

If you need any advice you can always message me or better yet join the Facebook group where a community can answer your questions!