Hei Bekko,
I use a mixture made with one litre of Formaline (a solution with 35 % formaldehyde) and 3.3 grames of green malachite.
In my pond I put 15 ml of the mixture for 1000 litre (my pond has about 12000 litre and I put 180 ml each two days and this, 3 times).
I had no sign of toxicity on the fish, but a put massive oxygen in the water from the day before the first treatment until two days after the last one.
I increase the temperature to 20 degree with a heater system and they had only a little food only the days without treatment and only once a day, just to see if the apetite was stil there.
That must be a concentration of 15 ppm of formaline and 0.05 ppm of green malachite, but I leave the week end to control ..
I bought a kin kikokuryu a few month ago, coming from Japan and he was one of the first to be hill, so it could be a costia problem . But I never detect them on microscope and I try a few time without results. Could be my foult that I did not see them, but I use the microscope every day in my work and I normaly know how to find such protozoaire.
I think I will never know for sure what was my problem, and that is a little frustration, but what a pleasure to see them getting better after only two days treatment.
So have a nice week end and enjoy your koi
