Paraguard vs Malachite Green or Methylene Blue


MFK Member
Dec 30, 2021
Have you tested your water?
If yes, what is your ammonia?
If yes, what is your nitrite?
If yes, what is your nitrate?
If I did not test my water...
...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.
Do you do water changes?
What percentage of water do you change?
How frequently do you change your water?
Every week
If I do not change my water...
...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.
I have used Paraguard, which seems to get rid of gill flukes reasonably well, and relaxes stressed fish well enough. If I use it on a small tank, I do not use that much of it, but there may be a case where I would have to use it on a large tank. Although it is good stuff, it is not particularly cheap. It is proprietary and imported.

I can get Malachite Green and Methylene Blue locally, and rather cheap too.

Could I treat with either one or the other, or both, and get similar - and safe - results as Paraguard?

Has anyone treated with Malachite Green or Methylene Blue, or anything else, and what was your experience?

Apart from price, what are the various pros and cons of the individual chemicals, or a proprietary brand?


MFK Member
Oct 1, 2012
Paraguard contains Malachite Green in combination with Glutaraldehyde. API SuperIck Cure contains Malachite Green in combination with Formaldehyde. You can tell the remedy contains MG if it turns the water green. IME, both are effective against ick, but scaleless fish are sensitive to MG and may die from full dosage. I am not aware of any commercial ick remedy contains Methylene Blue which, although is effective against ick, can impact beneficial bacteria. MB is used mainly to prevent egg fungus.


Redtail Catfish
MFK Member
Jan 30, 2007
If you have gill flukes you probably have skin flukes too. It's unlikely you will fully eradicate them, especially if you have a very large tank or outdoor pond.

You could move all fish into a smaller volume treatment tank and break the remaining flukes lifecycle without hosts. Also able to treat the tank with harsher medication once the fish are gone.

Use a microscope with skin and gill scrapes to confirm what flukes you have and later to know they have actually gone.

For treating flukes in larger tanks, I use Formalin/Formaldehyde and Malachite Green as per Noga's book of Fish Disease and Treatment. You will need to increase aeration. Then next outbreak I will use copper. Very stubborn strains require organophosphate (lawn grub killer) which will easily kill fish if mis-used. Switching treatments helps slow flukes resistance because they do adapt fast.

I make my own medications - feel free to privately message for individual advice. Copper for example is very cheap and effective but dosage will depend on your water hardness, pH and organic load.

Malachite Green on its own is quite toxic.
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