Brooklynella was named clownfish disease because it is most commonly seen in clownfish, but do not be fooled, as it can infect any fish. It is common in wild-caught clowns, but rarely seen in captive-bred clownfish, so better to ask your local fish store (LFS) whether their clownfish are captive-bred or wild-caught before buying. 

Brooklynella is a kidney bean-shaped microscopic parasite that is deadly to your fish, killing them in a matter of hours to days, so it is best to catch the symptoms early!