Confirming brooklynella
There are varying suggestions on how to treat an aquarium that has been infested with Brooklynella. They range from adding copper, malachite green, and other remedies, with some of those recommended being used in conjunction with formaldehyde. The best and most effective treatment for Brooklynella is formaldehyde alone. You want to go with a diluted version such as API Quick Cure which contains formalin.
Typically a standard formalin solution is mixed with either fresh or saltwater in a separate treatment container. Initially, all fish are given a quick dip in the formalin at a higher concentration, followed by continued treatment in a prolonged bath of formalin at a lower concentration in a quarantine tank (QT). Of course, the longer the fish are exposed to the formalin treatment, the more effective it will be at eliminating this disease.
If a formalin solution is not available for immediate use, temporary relief may be provided by giving fish a FW dip or bath. Even though this treatment will not cure the disease, it can help to remove some of the parasites, as well as reduce the amount of mucus in the gills to assist with respiration problems.
