[billsreef]

Flukes in a FW dip will turn opaque and fall off, making the dip container look like a snow globe if there are a lot of them. They can be quite common in fish from some wholesalers. If it is velvet, copper can be used during hypo with one caveat. You must raise the alkalinity to normal SW values. Hypo dilutes out not only the salt, but the buffer system and therefore lowers the alkalinity. Copper is more toxic at low alkalinity, therefore the problem with using it during hypo if you don't check and adjust the alkalinity to NSW values.