Formalin Malachite Green.
Our more detailed discussion including a video and more, is available to book owners at the following resource: Formalin and Malachite Green, Deeper.
Formalin is a mixture of formaldehyde “gas” in water that’s used to treat parasites in aquarium and pond fish.
It’s an odd chemical: For the manufacturer, it’s not an easy mix to stabilize and sometimes they use Methanol to make it more stable.
Formalin and Formaldehyde are essentially the same things. Formalin, by definition, is Formaldehyde at a concentration of 37% in water.
To use this, try to get “Methanol free”, but if not, you may have some trouble from your smaller treated fish (because methanol is stressful at least for a minute while it degasses).
If you can do a water change then consider this method although there are other ways to dose it:
Use 1 cc of Formalin 37% per 10 gallons to create a 25 ppm concentration in the system, wait two hours and flush out half the treatment water, sucking the outlet water from a bottom drain or vacuum the gravel if you’re dosing a tank. If possible, before treatment, remove the biological media to a fishless vat for the treatment period. Treat every day or every other day for three to five treatments for best results.
Our more detailed discussion including a video and more, is available to book owners at the following resource: Formalin and Malachite Green, Deeper. If you have the book you have access to the resource.