Discus Hexamita Disease – Metronidazole Complete Cure Guide

Discus Hexamita Disease - Metronidazole Complete Cure Guide

Hexamita is a type of small intestinal internal parasite consists of protozoa that have flagella affecting the gastrointestinal tract of a discus or other type of ornamental fishes, protozoa are unicellular microscopic organisms that might be parasitic to your fish.

Table of Contents

Can a Discus Fish Die from Hexamita?

Yes, it could cause your discus to die over time, even though Hexamita is progressed slowly, it is often associated with high mortality if left untreated. Hexamita causes severe intestinal disorders in fish. It’s believed that some Hexamita species are resistant to common medication such as Metronidazole which makes it hard to treat.

Non-sickness Reasons why discus fish is changing color:

  • Age.
  • Stress.
  • pH and temperature.
  • Fright.
  • Food.
NOTE: The above non-sickness reasons are making the discus color to change in general and not in a specific area if its body.

So, if you see that your discus turning white for other reasons like sickness, then you should follow the steps below information and steps to diagnose and treat.

Discus Hexamita Disease Symptoms

If you find any of the below symptoms on your Discus, chances are it is infected by Hexamita.

  • White stringy feces (white poop).
  • Hole in the head.
  • Discus body becomes thinner even though they’re eating.
  • Might lead discus to lose appetite.
  • Stay close to the aquarium heater.
  • Discus remains alone near the tank ground.
  • Signs of dropsy (might be shown).
  • Swimming in an abnormal way (if the brain is infected).
  • Discus fins look ragged. (along with the above symptoms)

Discus Hexamita Disease Details and Cause

The disease called Hexamita could show up on the fish due to continuous stress or by eating something loaded with Hexamita.

Hexamita is a bacteria exist in small numbers inside the gut of discus fishes, and since it is in small numbers, it’s ineffective and doesn’t harm the fish, but when the discus put in a certain environment that either:

  • Being stressed.
  • Being bullied.
  • Eating something loaded with Hexamita.
  • Placed in poor water quality.
  • Or being shipped for a long time.

Due to the above circumstances, the discus immunity system will work less efficiently and this will allow Hexamita bacteria to be increased rapidly and leave the discus gut to spread widely in its internal organs through the fish bloodstream.

So the risk of having one discus in your tank infected by the Hexamita will be hugely increased because flagellated protozoans will be reproduced within 24 hours only after being created, so when it’s established in a host like the poor discus fish, it will be spread very fast to other fishes in the tank.

NOTE: Metronidazole (Flagyl) which is the main chemical gradient of curing Hexamita infection of your discus, is basically an antibiotic that works a bactericidal action on gram-positive and some kind of gram-negative bacteria in a discus fish.

Metronidazole is well known for curing Discus fish infections like:

  • Hexamita.
  • Aeromonas.
  • Pseudomonas.
  • Mycobacterial (Gill diseases and Chondrococcus).
  • Anaerobic bacteria (a bacteria that grows only in a no oxygen environment).
  • parasitic diseases such as Cryptocaryon irritans.
  • Ichthyophthirius multifiliis.

Hexamita Treatment Steps

To beat the Hexamita bacteria in your infected Discus fish and tank you need to follow the below (metronidazole) Hexamita treatment instructions step by step, takin in consideration the important notes:

[METHOD 1] Treating Hexamita Using eSHa Hexamita

[STEP 1] – Remove Chemical Active Media From Your Tank Filter

Removing any chemical attachments from your tank filter is a must-do action as a first step, chemical attachments such as (carbon, UV, resins, oxidizers…etc) cause they influence Hexamita bacteria negatively as well as it will remove the effect of the eSHa (Hexamita metronidazole medicine).

NOTE: Keep your filter running without the chemical carbon and such all days and nights. 

[STEP 2] – Do Partial Water Change

This step has a special condition when it comes to water change before using the Hexamita treatment, so it is important to do a partial water change of 25 – 30% of your tank water before applying the eSHa Hexamita treatment (metronidazole) if your case matching one of the below cases:

  • Poor Water Quality: If you have a poor water quality then you should make a 25 – 30% water change before using the metronidazole treatment.
NOTE: It is very important to check your water quality occasionally using special testing kits to ensure a suitable environment for your Discus fishes.
  • A Water Conditioner Used: If you recently used a water conditioner in the aquarium, it is better to make the partial water change.
  • Another Treatment Used: In case if you tried another treatment recently while trying to remove the infection, then it is very advisable to make (2 x 50%) water change of your tank two times within a course of 3 days.
NOTE: You should not replace the whole water one time because you will remove a beneficial bacteria in the tank that a Discus fish cannot live without, do 50% water change, and after 3 days do another 50% water change then apply the metronidazole treatment following the below steps. Putting in mind to never clean your filter during this step cause the filter will supply some of the beneficial bacteria back to the aquarium.
  • Time Of Your Regular Water Change: If it is the time now to do your regular water change, then it’s better to do that before proceeding to the next metronidazole Hexamita treatment.
NOTE: It is very advisable to do a weekly based regular water changes to your Discus aquarium of 20 – 30% water change.

After you performed the water change, make sure to test the water quality with your kits.

[STEP 3] – Set Your Aquarium Heater To 30ºc

Set your aquarium heater temperature to 30ºc (86 – 88 f) as this will help the infected Discus fish to heal, remember that Discus fish has a good immunity system if you provide good water quality and high water temperature the fish will be able to expedite the healing process by its own due to the fact of increasing the metabolic rate in the fish body allowing the fish to absorb more medication internally.

[STEP 4] – Add Salt To The Water

Use aquarium salt or any type of salt that doesn’t contain iodine, before applying the medication to the tank, the dosage is (1 tablespoon for every 40 gallons of water).

Why adding salt to the Discus freshwater tank?

Adding salt to the Discus tank with or before the medication of the Hexamita will dehydrate the Discus fishes and this will lead there body will build up more bodied slime forcing the internal bacteria to go to the outside body of the Discus fish, thus they will be attacked more efficiently by the medication compared when they were inside the fish body.

NOTE: Do not put more than the said dosage as the more salt you add will harm the fish and make them stressful and this will not help in the treatment.

[STEP 5] – Apply The Metronidazole Hexamita Treatment

STEP 1 – Calculate Your Aquarium’s Volume

This is a very crucial step to take in order to use the proper dosage of the treatment accordingly, be sure to measure only the area that has water and exclude other areas like the gravel or the stones.

1 Liter = 0.22 Gallons, or 1 Gallon = 4.54 Liters

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for example, the water space of your aquarium is 50 cm length, 120 cm width, and 40 cm depth, so the calculations will be:

50x120x40 cm = 240,000 cm³

volume in liters = 240,000 cm³ / 1000

volume in liters = 240 Liters

NOTE: For gallons, it is the same principle but instead of 1000 divide the volume by 276 while the initial measurement should be done by inches

STEP 2 – Locate The Treatment Dosage Accordingly


Locate the eSHa Hexamita dosage in the medicine document, i.e. for the above-mentioned aquarium volume, we should use:

  • Day 1: 70 drops.
  • Day 2: 30 drops.
  • Day 3: 30 drops.
NOTE: The mentioned dosage was based on the example I provided above, for your case you should follow the dosage scale located within the eSHa Hexamita medicine box.

Put in mind as a reference for you, the standard dosage of eSHa Hexamita medicine (for 22 gallons / 100 liters) is 25 drops for day one, then 12 drops for day two and 12 drops for day three.

STEP 3 – Apply The Dosage To Your Infected Aquarium Tank

To apply the Hexamita medicine into your aquarium you need to hold the drug bottle upside down and by squeezing the pipette, count the number of drops you are adding to the tank water hence (1ml = 20 drops) till you complete the proper dosage.

NOTE: The 20 ml Hexamita bottle can complete a 3-day course of treatment to a maximum of 175 gallons (800 liters) aquarium, so if your aquarium is bigger in size you better either buy more than one bottle or bigger bottle size.
TIP: In some cases where you were so late in ordering the eSHa Hexamita or you discovered the discus illness in late-stage you can double or triple the standard medicine dosage to give a fast initial result but remember this is only of the infection is on late-stage or it is so serious.

[METHOD 2] Treating Hexamita Using API General Cure Powder

[STEP 1] – Prepare The Metronidazole Dosage

Prepare the powder in a cup by using 1 gram for every 20 gallons of your tank water.

NOTE: This is based on your tank size, you could calculate your aquarium tank size from the previous method steps.

[STEP 2] – Mix It With Water

Mix the prepared powder dosage with the water in the cup then pours it into the tank.

[STEP 3] – Repeat This Medication

Repeat this medication every 8 hours for 10 days even if you see improvement within 5 to 7 days to prevent Hexamita hatchlings inside the discus guts.

[METHOD 3] Treating Hexamita By Mixing It With The Food

If you see your discus is still eating you are lucky, cause this method of treating your ill discus fish is 10 times more effective than the previous methods.

[STEP 1] – Prepare The Metronidazole Dosage

Prepare the same amount of the API Metronidazole powder using 1 gram for every 20 gallons.

[STEP 2] – Mix The Metronidazole With The Food

Mix the metronidazole powder with the food no matter what type of food you are feeding your discus.

NOTE: you can watch the below video on how to mix the medication with your discus food.

[STEP 3] – Repeat This Medication

Repeat this medication every 8 hours for 10 days even if you see improvement within 5 to 7 days to prevent Hexamita hatchlings inside the discus guts.

[METHOD 4] Treating Hexamita Using Alternative Medication

If you are not able to apply the previous methods for any reason, you could try alternative treatment from different products by following their treatment steps that you find in their instructions book.

  • Seachem MetroPlex
  • Thomas Labs Fish Zole

Future Prevention Tips

Take the below prevention tips in the future to prevent your Discus from being attached by a parasite or bacterial infection.

  • Do not put a newly purchased Discus or fish in your main tank, always have another hospital tank to put the new fish in it for several days to ensure it is clean from any infections. put in your mind several infections do not appear on the skin or on the fish behavior so you will not know if it is infected or not from the first day.
  • Before presenting the new fish to your tank, be sure to mix the new tank water with its current water in a bag or so and keep it for 15 min so the new Discus can acclimatize the new water quality and ingredient, thus reducing the possibility of putting her in stress.
  • Keep an eye on your water parameters using special test kits for different readings like pH, ammonia, nitrate, nitrite ..etc, in this case, you will create a healthy environment for your Discus fish to live healthily.
  • Do a weekly 25 – 30% water change for your aquarium to refresh the water quality and keep your water clean.
  • Always put an air pump to your Discus aquarium and keep it on 24 hours all the time, this will provide sufficient oxygen to your fishes, and reduce the chance for some harmful bacteria to be built.
  • Do not feed your Discus frozen worms, a lot of Discus owners are complaining to have infections and issues with their Discus after feeding them frozen worms, while many other providers and owners say it is fine with frozen worms, but since there are a good amount of Discus owners complaining and having issues, I advise you to stop feeding your Discus frozen worms to clean this issue up.
  • Do not feed your Discus flakes, flakes are used as a feed to all type of clear water fishes including Discus but, from my experience when putting flakes in the water it will float on the water surface, this will lead the Discus to eat it while it is floating, and this scenario might cause the fish to enter air to its stomach and will cause an issue called swim bladder disorder, and it will be a pain in the ass to heal the fish if in case it was healed successfully, sometimes this leads the fish to die cause she will no longer be able to eat.
  • Clean your filter every 1 month or month and a half, using an ammonia test kit in your aquarium water can help you to identify when it is required to clean the filter, this way you will keep non-toxic water.
  • When you see any starting symptoms in any Discus, do not wait till the symptoms increased but react quickly to clean any disease from the tank, so keep an eye on your Discus fishes daily.


This is me Firas Sameer, the founder of DiscusRescue.com, I am an aquarist guy with a passion and love for Discus fishes, I am learning every day with my hobby at home and sharing the things I am learning from my experience with you.

15 thoughts on “Discus Hexamita Disease – Metronidazole Complete Cure Guide

  1. Hi Sameer. Professionally managed one stop destination for rescuing Discus. The subject has been covered in detail and collated beautifully. Thank you for sharing the details. If u have any channel on Youtube, i would like to follow it as well.

    1. Thanks Joe for stopping by at our website which is, in the end, is your website, unfortunately, I do not have a youtube channel for this website.

  2. Hala Firas,

    It’s simply amazing stuff and making our life easier. I had a question about using Flagyl 400mg metronidazole from a human pharmacy. is that ok to use it? if yes please let me know-how

    Many thanks in advance

    1. Hi Mohammad,

      Yes, you can use Flagyl 400mg for treating Discus fish, but, it won’t be that much effective, however, if you want to use it then it’s better to separate the Discus in a smaller tank and double the dosage.

      how to use Flagyl 400mg for Discus?
      simply by following the below steps:

      remember the dosage of 1 gram for every 20 gallons of water.

      NOTE: in this case, every 2 tablets and a half should be 1 gram.

      1- Chopping the tablets using a knife try to make them like a powder.
      2- Use a small cup with the tank water and mix that powder very well in it.
      3- Then pour the whole water of the cup into the tank.

      I have tried this before, the result is very less especially if your Discus having a severe infection, and the reason why because it is not designed to melt very well in water like the proper medicine.
      so better to try the real medicine as described above from the link.

      Good luck.

      1. Thanks for your reply.
        I I ordered eSHa Hexamita. But it will arrive to dubai by end of the month. For now I use API general cure with ebsom salt. But it’s really expensive here because I treated the whole tank 100 gallons so I used 20 pack of general cure to complete the course.

        1. Good for you, eSHa Hexamita is very powerful, you will see a big difference when you use it treating Hexamita in your Discus.

  3. Hi mate, I wanted to ask for your advise. I’m going to start treating my discus with metronidazole but in 2 days my esha hexamita that I ordered will arrive. Should I still continue the 10 days of my metronidazole treatment or I can stop once I commence with the esha hexamita?

    1. it depends if you see any improvement against the Discus Hexamita, you should see some improvement as the main ingredient for treating Hexiamita is Metronidazole, otherwise, you could try the Esha Hexamita you purchased after isolating your infected Discus into a separate tank then apply it for 3 days.

      Good luck.

  4. Hey Firas!

    Thank you for such an outstanding article isolated to specific treatments.
    One question for you – If using metroplex by Seachem, the included scoop is 125mg, which means per your treatment dosage instructions, would be 8 scoops of this med per every 20 gallons (whether dosing tank or in food). And for API general cure, one packet is 325mg (ratio of 250mg metro/75 prazi) which with your dosage instructions translates to 3 packets (975mg) per every 20 gal (whether dosing tank or in food). And these amounts are to be administered every 8 hours for ten days.

    There are only 5grams in a metroplex bottle and ten packets in an api general cure package, so thats a lot of medicine used for larger tanks. In my current case I have to treat all my discus in a 70 gal tank.

    Is my math right, and should I be comfortable with dosing this amount at this rate, or am I missing it? Also in the medication/food ratio are you feeding that medicine and food per what your fish will eat or trying to feed that given amount every feeding every eight hours?

    Thank you so much, from one discus keeper to another.

    1. As I mentioned in “[METHOD 4] Treating Hexamita Using Alternative Medication” above, you need to follow the instructions attached in the medication box, however, I highly advise you to use Hexamita for a real result.

  5. hi sameer
    first i want thank u for sharing your experience in treating discus. as you mentioned, metronidazole is an antibiotic medicine so could it harm fishes internal organes? i read somewhere that using medicine incorrectly could harm the fish and stop it’s growing naturally!
    on the other hand, after using antibiotic, fishes in the tank became weak and thin! how i should behave to making them strong again? should i add any vitamins and mineral to their food. i feed them with mix of meet and garlic and shrimp which made is home made.

    1. When your fish is sick, you have no other way but to use the proper medicine, if you believe the antibiotic or any other medication that should heal your fish, then you have no other option to heal your sick Discus.

      besides, medicating your Discus will not stay forever, hence, no need to worry about your Discus not going to grow..etc, its a matter of a couple of days of treatment, otherwise, its up to you and I wish you luck.

  6. Everytime i cure it with metronidazole or any fish medicine for hexamita it gets cured but i see new hole within a week is there anyway i can stop it from coming back im feeding it discus bio gold and Australian blackworm and i do 50% water change every 3-4. Days

  7. Hi there,

    one of my juvenile discus, has symptoms of Hexamita and doesn’t seem to eat. I would like to treat the whole tank with esha Hexamita , but I m afraid that it will be too much for my snails. What are your thoughts on that?

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