Malachite Green & Formalin should not be used when the salt level in the pond is higher than .1% unless you know for a fact that the pond water is very soft. If the pond water is hard at all and the salt level is above .1%, the use of formalin can severely burn the gills of the koi. Malachite Green & Formalin can kill the beneficial bacteria in the biological filter, so if possible, bypass the filter for at least 8 hours during use. Malachite Green & Formalin can kill plants, so if possible, remove all plants while the pond is being treated. The plants should be treated with potassium permanganate separately before returned to the pond. (To treat pond plants for parasites, mix up a solution of 3 tablespoons of potassium permanganate dissolved in 12 gallons of water. Allow the plant root ball to dry out slightly and then completely submerge the plant root system in the solution for 2 hours.)
To treat ponds up to 1500 gallons.
Measure out enough Malachite Green & Formalin to treat the whole pond at a dosage of 10 ml per 100 gallons. Drain 50% of the water out of the pond, and then add the Malachite Green & Formalin to the pond. After exactly 2 hours, refill the pond as fast as possible to its normal level, and don’t forget to add dechlorinator. You must refill the pond within 45 minutes, or you risk the chance of burning the fish’s gills. Perform this treatment three days in a row. If you have costia, we recommend treating four days in a row, a rest day on the fifth day, and then once more on day six. If the pond refills with city water, remember to add dechlorinator to the water to remove chlorine in the new water. This technique is very effective because it exposes the parasites to twice the dose of medication for 2 hours, which is usually enough to kill them.
To treat ponds over 1500 gallons.
The above treatment should not be performed on ponds over 1500 gallons because it takes too long to refill the larger ponds. In this case, we recommend performing a 25% water change before each treatment. If the pond refills with city water, remember to add dechlorinator to the water to remove chlorine in the new water. After the pond refills to its normal level, add the Malachite Green & Formalin at a dose of 10 ml per 100 gallons. Treat the pond four days in a row. If you have costia, we recommend treating one more time on day six.