Formalin is a very effective and cheap medicine for all Protozoal diseases and external parasites, but should never be used with high concentrations of salt. The active ingredient is Formaldehyde.

For best results, it should be mixed with Malachite green (combined known as FMC or F & M) which makes it a very effective and recommended treatment for Trichodenia, Chilodonella, Costia and White spot.

FMC Mix: 100 mg Malachite Green and 15 ml Formalin per 1000 liters. (Some people also mix 100 mg Methaline blue into the mix)

It should not be used in water temperatures below 10 degree Celsius and it is extremely important to use the correct dosage, as it is a dangerous medicine and you will kill your fish if you overdose.

If you have goldfish in the pond, you should use 50% of this dosage.

Paul, just a question on white spot.

3 Weeks ago i discovered that some of my koi had some white spot...it seemed that i caught it very early. I have never had whitespot in my main pond before so this is a first for me - i always killed the buggers off during my quarintine procedures but now that it is in my main pond it is working out a bit expensive to get rid of it.

I did 2 treatments of M & F 3 days apart. The instructions on the M & F read: 15ML / 1000l. That is 480ml of M & F per treatment for me and 200ml of M & F = R 50. That is roughly R 150 per treatment.

Are 2 treatments good enough?

I heard and read that Whitespot is very difficult to erradicate because the adult parasite that is in its reproduction face is immune to the treatment.

When whitespot has reached its mature state(when you can notice it without a microscope), it is difficult to kill them as it is embedded between the top two layers of the skin. You must try to kill the free swimming stages, and therefore you need to treat at least three times, with a few days inbetween.

That is really the last thing i need...to be disqualified / rejected from the show due to white spot on my koi...especially since this will be my first year...I have been waiting 3 years for this.

I have a black koi in my pond which i use to do scrapes and things on, the black color of the koi also makes it easy to see if anything is wrong in the pond.

I run outside quickly and took a few scrapes from it and so far i am happy that nothing is visible on it and i can't find anything under the microscope.

Do you mix your own M & F? Which part is responsible for actually killing the parasites? M or F? Isnt Formalin an anti fungal product?

Both Malachite green and formalin iare for Protozoal diseases like White spot.

Malachite green is often enough to kill White spot, but your success rate is better if mixed with fomalin.

Formalin is an all round anti-parasite and general pond treatment and will probably not kill the White spot if used without Malachite green.

As said above, you can also mix Methaline blue into the mix to increase your success rate even more. The "classic mix" contains all three.

I do my own mix of Formalin(150ml) and Malachite Green (1g) and sell it for at least half of what you pay. You are welcome to pop in next week(I am going away for a few days)

Salt @ 0.5%

What is the reason for not using Formalin and salt together?

Very little info on the net except that many sites warns you not to use salt with formalin. Bit confusing to me since they use formalin in salt aquariums as a medicine.

I'm so thankful I'm aware about this.Not to use formalin in salt ...


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Hi,

The combination of formalin and salt strip the Koi not only from its Cuticle ( consisting of mucus, antibodies and lysozymos) but also of the Epidermis ( Malpighain cells) and Goblet Cells ( mucus secreting) which leave the Koi unprotected to infections, sometime called as skin burn. Also damaging the gils.