The tomites swim into the water column in search of a host and, failing to find one, die in a short time. If they do find a host, the tomites attach and encyst. The life cycle is temperature dependent, and can occur in 3 to 4 days at 70 dF and up to five weeks at 50 dF. At lower temps, the parasite will remain dormant. As long as the parasite is encysted on the fish, it is immune to treatment. However, at the first notice of these cysts, treatment should be started.
Malachite green is generally safe to use for most freshwater species.
I know some of you must be shaking your heads, saying that malachite green will kill some freshwater species. When dosed correctly, malachite green is safe for even the most so-called sensitive species. The correct dose is 0.05 ppm malachite green for three treatments, one every other day. At this level, your fish should not experience malachite sensitivity. Of course, dosing at 0.05 ppm means doing more than adding one drop per gallon.