Shrimp Disease – Scutariella Japonica. Treatment.

Scutariella Japonica on the shrimp head

Today we will talk about a shrimp disease called Scutariella Japonica. It seems to be the most common shrimp parasite. You will know why it can happen to your shrimp, how you can identify it, ways of treatment (Freshwater aquarium salt, Seachem ParaGuard, Praziquantel, Fenbendazole, Internal Parasite Clear, Benibachi Planaria Zero and No Planaria treatment), and how to prevent contamination of the rest shrimp colony.

The shrimp hobby has grown a lot in recent years. As a result, it has created a huge demand for shrimp. Unfortunately, local shrimp shops are not able to meet this demand anymore and have to import shrimp.

Here comes the bad news. The main problem with the imported Neocaridina shrimp is that they are not bred in a closed environment. Thus they are showing a bigger prevalence for the disease. Lucky us but most of the tigers, bee, crystal shrimp are still being bred inside but for how long it will last.

How to identify Scutariella Japonica?

The first thing to look for is the small white 1 to 2 millimeter branchy appendages on top of the shrimp’s head, and down the rostrum. These parasitic nematodes are called Scutariella Japonica (Classification – Plathelmintae/Tubellaria/Temnocephalidae/Scutarielloidea). They are flatworms (similar to planaria).  However, they behave differently.

ScutariellaThe parasites usually live in the gills or mantle of the shrimp. They generally attach themselves somewhere between the eyes or on the shrimp’s rostrum. It is very rare to see them on shrimp legs and other body parts.

scutariella eggsThe second way you can identify them is by looking for eggs in the shrimp’s plate. The parasites are very clever, they lay their eggs behind the head on the gill chamber in little rows (white dots).

When the shrimp changes its exoskeleton, the eggs are released and, after being born, they colonize another host.

Usually, you can see them even with the naked eye without any special tools for that.

Scutariella Japonica is usually confused with the protozoa Vorticella. Although they have nothing in common at the taxonomic level. An easy way to differentiate them is by color: the Vorticella is transparent or almost transparent while the Scutariellas are opaque, in addition to white.

Structure of Scutariella Japonica

If we observe the parasite with a magnifying glass or magnifying lens, we can see that on the one end this flatworm has a sucker to attach to the shrimp’s shell. While on the other end it has a kind of primary tentacles. The parasite feeds on the plasma of the host shrimp and detritus contained in water exhaled from the gills.

Is Scutariella Japonica dangerous to the Shrimp?

Scutariella Japonica is actually rather harmless to the shrimp. It will not actually kill the host or really cause it any damage.

Unless they get in really high numbers. In this case, the parasites may even cause casualties since they interfere with the breathing and mobility of the shrimp, causing destruction to the host body structures (According to the study “Parasites and Wildlife First molecular identification of Vorticella sp. from freshwater shrimps in Tainan“, Taiwan).

Observation shows Scutariella japonica can use shrimp as its own mobile base (for example by attaching itself to the rostrum) to obtain organic material from the water column as well as living its parasitic lifestyle using shrimp as its host (for example attaching to the gills).

Thanks to this ability to adapt Scutariella japonica can be dangerous to the aquarium shrimp keeping as it can easily infect not only weakened individuals but also healthy ones.

Possible causes: unclear but most likely because of poor water conditions.

Name Scutariella Japonica
Type parasitic nematodes
Threat level Low
Treatment difficulty Easy
Treatment efficiency 100%
Treatment cost 3-25$
Treatment length Up to 3 weeks (because of the eggs)

Scutariella japonica adults saddle in Neocaridina davidi rostrum

How do you treat these parasites?

1. Freshwater aquarium salt vs Scutariella Japonica.

Aquarium saltThe first way to remove this parasitic trematode is to use salt. Freshwater aquarium salt (link to check the price on Amazon) would be the safest choice. Although you can use table salt as well.

Some shrimp breeders categorically do not advise using the salts that we use at home because these salts contain potassium iodine. For us, for humans, the potassium iodine is very important so we will not get thyroid disease. However, for shrimp…

I have spent lots of time trying to find any scientific studies that showed that shrimp need iodine from the water column. I did not find any. Neither could I find any that demonstrates that they do not need it. We only know that shrimp get most of their iodine from the food, and even then, the amount required is minuscules.

Proper usage method # 1:

  1. Take 1 tablespoon of salt and add it to a cup of aquarium water.
  2. Dissolve the salt in the water by stirring it.
  3. When it is completely dissolved, take the infected shrimp out of your tank and put it into the cup for about 30-60 seconds.
  4. Then remove the shrimp and put it back to your aquarium.
  5. Remove molts for the next 2-3 weeks.

There are two downsides of this method:

  1. In the case of fully developed infestation, there is a chance that you will only reduce it after 1st dip. So you will need to keep this shrimp somewhere until the 2nd dip (meaning 1 dip each day).
  2. The main downside of this method is that you have to catch every infected shrimp and it can be very problematic. Especially when you have a big aquarium and a lot of shrimp. That is why some advanced shrimp keepers (like Robert Lupton – Flip Aquatics) propose another way (method # 2).

Proper usage method # 2:

  1. Take 1 tablespoon of the freshwater aquarium salt per 5 gallons of water.
  2. Increase dosage as needed.
  3. Water changes each week of 20%
  4. Remove molts for the next 2-3 weeks.

That removes all the visible external parasites. Scutariella Japonica will be gone from the shrimp’s body. I have seen no shrimp mortality using this treatment. Unfortunately, saltwater does not have any effect on the eggs of the parasite and you will have to deal with them later.

Tip: The Asian Journal of Animal and Veterinary Advances also recommends treating shrimp in slight saline conditions (5–10 ppt) to prevent infestation and mortality.

2. Seachem’s ParaGuard treatment vs Scutariella Japonica

Bottle of paraguardInstead of treating each shrimp, you can treat the whole tank. You will hear and read about this medicine almost in every article about shrimp diseases. ParaGuard (link to check the price on Amazon) does not seem to harm shrimp or shrimplets. Seachem’s medicine does not contain formaldehyde or methanol and it will not change the pH of your water.

Proper usage:

  1. Recommended dose *5mL (1 capful) to every 40 Liters (10 gallons)
  2. Repeat daily for about a week.
  3. Remove molts for the next 2-3 weeks.

The bad thing is that ParaGuard does not take care of the eggs as well. In some cases, people use ParaGuard after salt treatment just to make sure and reduce the chances of spreading the disease. Unfortunately, it is very pricey.

*WARNING: Although even advanced shrimp breeders recommend using it, nobody says that Seachem has admitted that the Paraguard is not invertebrate-safe.

Quote “ We do not sell or market ParaGuard™ as invert safe because it would be impossible to test it with every available invert under every potential water parameter. We have had people use it with invertebrates with no problems, but we have also had people encounter problems. If you decide to use it we stress caution; dose at 1/4 to 1/2 dose and observe how your inverts and soft corals react. If they seem to tolerate the dosing, increase slowly up to no more than the prescribed dose as long as they are tolerating it. If you need to get rid of the ParaGuard™quickly, just turn your skimmer back on.”

3. Praziquantel treatment (Tremazol von Sera, Teniciven, Zipyran) vs Scutariella Japonica

Botlle of PraziquantelThis is another way to treat the whole tank. Although the product was not designed for aquarium purposes, it still gives great results against parasitic worm infections like this one.

The Praziquantel attacks the nervous system of the parasite. As a result of paralysis, the parasite will release the hook with which it grabs the shrimp. The Praziquantel also acts by making the skin of the worm very permeable, causing it to lose glucose until death.

According to AMAZONAS Magazine (July/August 2015), some shrimp keepers recommend using Praziquantel:

  1. Optimal dose 2,5mg per 1 Liter (10mg per 1 gallon).
  2. Repeat the dose after 2-3 weeks to eliminate the parasite from hatched eggs.
  3. Remove molts for the next 2-3 weeks.
  4. Water change 30-40% after treatment.

There is no need to repeat it more often. The medication is quite powerful and at the same time, it is quite safe for the shrimp.

Tip: during the treatment, it is advisable to maintain strong aeration. Praziquantel is a drug that consumes a lot of oxygen, so if you have CO2, you will have to monitor it closely.  Read more about it in my article “CO2 in a Shrimp Tank”. There is no information on the internet on how this medicine can affect snails. I would just take them out to be safe.

4. Fenbendazole treatment vs Scutariella Japonica

Yet we see another medicine (Panacur C and Canine DeWormer (link to check the price on Amazon)) which aquarist use at their own risk. It is almost the same as with planaria treatment. Be careful with snails if you have them and they are part of your eco-system. Because Fenbendazole can be lethal for them.

Presumed dosage and usage:

  1. Use 0,1g per 10-gallons of liquid fenbendazole.
  2. Repeat the dose in 2-3 weeks to eliminate the parasite from hatched eggs.
  3. Remove molts for the next 2-3 weeks.

5. Internal Parasite ClearBenibachi Planaria Zero and No Planaria treatment vs Scutariella Japonica

Noplanaria and Planaria zeroThese are the last products in my list, which can remove the disease according to SKFA members ( Frankly saying, they are less popular and there is no much information about dosage for our cases.

Nonetheless, I want to tell you guys about all the methods which worked for different people. Because sometimes even the most popular ones may not work for you while the rest will.
Suggested dosage and usage:

  1. Use half of the dose as per instructions on the packaging.
  2. Repeat for 3 days. Although you might see the pests disappear after one day, continuing treatment will ensure any unseen parasites are also killed.
  3. Perform a 30-40% water change at the end of the treatment.
  4. Remove molts for the next 2-3 weeks.

Tip: Better to remove your carbon filter before dosing.

Benibachi Planaria Zero – link to check the price on Amazon.

Removing the Molts

When the shrimp molts the parasites or eggs are generally attached to the molts rather than the shrimp themselves. That is how they spread.

You will have to remove the molts as fast as it is possible from the aquarium for at least 2 or 3 weeks in a row after any treatment. If you cannot stay around your aquarium all the time do it at least twice a day in the morning and in the evening.

Otherwise, once the eggs on the shrimp molts are hatched they will re-infect the entire colony again.

Tip: do water changes on a day when you know that you are going to be home during the next few days. For example, if you plan to stay at home during the weekend, you can do the water change on Friday. The thing is that water change is one of the triggers for the molting process of the shrimp. Because it is a stress for the shrimp. Thus, there is a higher chance of shrimp molting during those two days when you are home and you can remove these molts almost immediately.

Tips for Prevention of the Disease

  1. Always try getting all your shrimp from domestic breeders. It is faster, safer and you can check them on the spot.
  2. It can be hard to notice Scutariella Japonica at the early stages of the infection. That is why you can take macro photography or look at it close up with the SLR camera with a macro lens.
  3. Ask the importer about their quarantine protocol policy.
  4. If it is possible, do 30 days quarantine yourself. If you have some doubts about new shrimp, it is better to play safe. When you get your shrimp look at them really carefully. Do a prolonged quarantine in order to ensure their health.
  5. Use additional methods to improve the immune system of the shrimp as Indian Almond Leaves, Alder cones and etc.


The information has been taken from magazines, forums, blogs, documents from American, German, Russian, and Spanish shrimp breeders. I tried my best to find all these treatment guidelines that have given me the most confidence and I cannot be held responsible for any problem which can arise.

Because their effectiveness (or danger) may also depend on other parameters such as water conditions, the global state of our shrimp, conditions of maintenance, other chemicals present, etc … I have limited myself to verify the most frequently mentioned and most valued, nothing more.

Read also my article “Understanding Dwarf Shrimp Diseases and Parasites”.


33 thoughts on “Shrimp Disease – Scutariella Japonica. Treatment.

  1. Really helpful and thoroughly documented. Much appreciated.

    1. Hi Angelo,
      Thank you! I am glad to help.
      Best regards,

  2. Thank you for all the information. It definitely helped

  3. Hi Michael, Greeting from Indonesia
    Your writing have become my no 1 source in shrimp keeping.

    i wanna ask if Freshwater aquarium salt cause TDS to spike?
    should i add it gradually or just put 1 tablespoon per 5 gallons of water right away?


    1. Hi aprianto,
      Thank you!
      TDS includes almost everything that we put and use in our tanks – mineral, salts, nitrites, nitrates, ammonia, dechlorinator, water conditioners, fertilizers, wastes, etc.
      Therefore, freshwater aquarium salt will also increase TDS number but your dosage should not cause TDS to spike.
      The increase and spike are not the same.
      Best regards,

  4. Hello, thank you for the article, I found it very detailed and helpful!

    Regarding the salt treatment, in method #2 (tank treatment) you mention 20% water changes each week. Is this meant to gradually restore the water salinity to previous levels, or not? If not, I can prepare a large enough volume of salty water (with the specified concentration) to use it for water changes during the treatment time. Right?

    This is the end of week one, and I still see marks (small parasites or eggs) on shrimp heads. Would it be a good idea to combine the treatment with Paraguard, or could it be too stressful for the shrimp?

    Thanks in advance,

    1. Hi Harilaos,
      Yes, it should be done to gradually restore the water salinity to previous levels. Sorry, but are you going to do water changes with salty water? I am a little bit confused. What is the point?
      Personally, I would not do different treatments at the same time. It can be too much stress for the shrimp to handle.
      Best regards,

  5. Hello Michael, thank you for your reply!

    I wasn’t sure what the 20% waterchange was for (that’s why I asked), so I was stating my options the way that I understood them. In case salinity was to be kept stable over the course of 2-3 weeks, that would mean a different route, but since you say waterchanges are meant to gradually decrease salinity, I’ll follow your advice.

    The parasites have not been totally removed yet, so I guess I’ll have to wait two more weeks to see if another tratment is in order.

    Thanks again!

  6. My oldest cherry almost a year old now had a few of these things on her face a few days after molting. She was the only one in the tank I could see with them. So I tried the saltwater dip method on her and the damn worms came off in the saltwater immediately. As soon and she settled in the tank I couldn’t see any of them on her anymore. Thanks for the advice!

    1. Hi Mark Davenport,
      Thank you for the feedback as well!
      Best regards,

  7. (Trying to post this question again… seems it didn’t work the first time.)
    I just bought some of the Praziquantel treatment (I got Aquascape’s like you have pictured but the bottle looks a little different). I noticed you say to dose 10mL per 1 gallon. I zoomed in on the directions on the bottle on Amazon (I’m still waiting for mine to arrive) and it says to dose 5mL per 25 gallons. That’s quite a bit different. Just wondering if I should follow your dosage or if there was a typo. Thanks!!

  8. Thank you so much for the quick reply! I just had to check to make sure. And I love Rachel so I’m going to trust it. Fingers crossed!! Thanks again. Appreciate it.

    1. Actually I just looked at her article and its says 2.5mg (not mL!) per L. which is the same roughly as 10mg/gal (way different than mL). Look at it again you might want to change that to mg. If my math is correct it is less than the bottle’s recommendation of 5mL/25gal – I got around 3mL but I need to check that math again.

      1. Hi TC,
        You are absolutely right. That was a bad typo. Sorry.
        Best regards,

  9. Wow, fantastic blog! The overall look of your site is magnificent, as well as the content!

  10. Seachem’s own site says Paraguard “should not be used in tanks that contain plants or invertebrates”
    I don’t know why the above is getting flagged as spam. Tried five times.

    1. Hi Christina H,
      I have a very strict filter.
      It may flag even good comments as spam. Nolnetheless, I check them anyway.
      As for your statement, well, I have a full paragraph about that in the article.
      Also, there are not many ways we can treat shrimp deseases, therefore, shrimp keepers often use methods that can be potentialy harmful.
      Best regards,

  11. I have three neocardina shrimp have white areas inside their bodies on the upper back. I have removed them from the tank but I don’t know what to do. They seem to be ok otherwise. This is my first time with shrimp so I am completely lost. Thanks for any help. I have pictures but I can’t load them

    1. Hi Patty,
      I have sent you the message. Check your email, please.
      Best regardss,

  12. Hi, just wondering if this salt bath concentration is safe for juvenile shrimp?

    1. Hi Ax,
      I have not had any problems with that.
      Anyway, juveniles grow really fast, so they molt often. As a result, they raraly have these parasites on them. Just remove molts.
      Best regards,

  13. Hello!
    I believe I have the beginnings of scuteriella in some neocaridina. It is only one or two little white stalks per shrimp. One has leg joints that look bright if that makes sense. I don’t want to treat the bowl if it’s just natural variation. I have some Nerites in there so I was going to start with salt. Can I send in a few pictures? The bowl is almost perfect and stable and I don’t wanna damage the Monte Carlo or red root floater with salt, if I don’t have to.

    1. Hi D,
      Sure, I have sent you a message, check your email, please.
      Best regards,

  14. Hi
    Just a quick question on method #2
    Do I add salt dose each day for a week then water change or only dose the once then water change?
    Thanks for your time

    1. Hi Sall,
      Initially, I described the single dose that needs to be added to the tank.
      As for water changes, to maintain the concentration (during treatment), you will also need to mix in the corresponding portion. For example, with a 20% water change, you will need to add 1/5 of the initial dose.
      I would NOT recommend adding salt every day because you can quickly create an excessive concentration.
      Best regards,

      1. Hi again
        I’m in Aus and work with metric,my tank is 9 litres so would you say 2 gallons ? And use just under half a table spoon of salt?
        Salt treatment for fish here is 1 teaspoon per 5 litres wondering if that’s around the same rate.
        Thanks again for your time

        1. Hi Sally,
          Well, something like that. You need a little less than a tablespoon, but even if it’s half, there won’t be a significant difference.
          As for your example with the fish, they are more tolerant to changes compared to shrimp and can withstand higher doses.
          Best regards,

  15. Hello, I’ve noticed these on my shrimp as I was taking some macro photography!
    I have a 29 gallon planted tank with tetras, pygmy Cory’s, bristlenose Pleco and snails.
    What’s the best way to start a treatment to ensure this doesn’t get out of control?

    1. Hi Mark,
      Depending on the quantity of infected shrimp, if there are only a few, I would recommend starting with salt baths for them.
      Best regards,

  16. I have some neos, they have these parasites and I was wondering if they are inside the shrimp will they get out in the saltbath?

    1. Hi Matias,
      What do you mean by “will they get out in the saltbath?”
      Best regards,

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