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How to Take a Mucus Sample/Scrape

The first step to koi parasite identification is taking a mucus sample or scrape. A mucus sample is examined under a microscope to correctly identify the exact parasite/s affecting your koi, so the right treatment can be administered swiftly, saving time and money.

Taking a mucus sample/scrape is a simple task that all koi keepers will have to do at some point. It’s easy and quick, though can be daunting for beginner koi keepers. Done correctly, it poses very little risk to the koi. 

You will at least need some basic pieces of koi handling equipment to safely take a scrape. A good quality net, bowl, and possibly a koi sock will be required. You will also need a plastic card (points card, fuel card, bank card etc), microscope slides and cover slips. It’s good to own a quality microscope, though borrowing from a friend or koi club, or bringing a sample to our shop is an option. 

Let’s look at the steps for taking a scrape:

  1. Identify a sample of koi to examine. We recommend 3 koi minimum, usually the fish that you suspect are affected.
  2. Prepare equipment. Have your net, bowl, sock, and plastic card to hand. 
  3. Catch the first koi to be examined. 
  4. In a bowl with just enough water to cover the fish’s gills, turn the koi upside down and using the plastic card, scrape gently from the underside of the head to the belly of the fish. Return the koi to the pond.
  5. Transfer the mucus to the slide, and place the cover slip on top gently. 
  6. Repeat steps 3-6 for the remaining koi.
  7. Examine mucus under the microscope. 


Top Tips: 

  • It’s handy to keep some Kusuri Masuizai Koi Sedate by the pond when taking scrapes, sometimes koi can be a little agitated in the bowl, and a calm koi is less likely to be damaged. 
  • Taking a sample from underneath the koi is easiest when taking scrapes alone as koi are generally motionless when turned upside down. You can also take samples from the flank (from the gill opening to tail), or from the top of the head. 
  • When bringing samples to the shop for examination, use a sealed food container so the sample stays moist. Don’t use plastic bags which just makes a mess. 

Now you have your sample, it’s time to examine the mucus under the microscope! 




If you don't have all of the items already, we stock almost everything you might need:

  • Bowls and Socks
    • Koi Pan Net (this is the big circular net seen in the video - you should get one suitably sized for your largest fish and with a handle that enables you to reach all of your pond)
    • Koi Sock (this is the shorter net used in the video to safely carry the fish from the pond into the bowl - these are generally one size with variations on handle length and how much water it retains during movement)
    • Koi Bowl (this is the bowl on the floor in the video that is used to temporarily hold a fish for inspection/measurement - you should size this to suitably hold your largest fish)
  • Koi Sedate (This is used to calm an agitated fish for the purposes of inspection, treatment and measurement - you should pay close attention to the dosage requirements and you only need use it if you feel you need to)
    • We are able to offer this at better value as part of a treatment set for topical treatments and would recommend that you purchase the following for a better value purchase.
  • Microscope Slides
  • Microscope Cover Slips
  • Microscope -whilst we don't currently offer one ourselves, there's a great value scope available called the "Apex Practitioner" available from many places.