Brook question

[Naraku]

I will have rainfordi arriving Wednesday.

I will be doing tank transfer with a formalin bath before going into quarantine.
Will brook be eliminated with a formalin bath of 50 min or should I do more formalin baths between transfers.

I don't want to do too much formalin since it is carcinogenic.

 

[ThRoewer]

Unless the fish is visibly sick with brook one dip should be enough.

As for the carcinogenic part:
"... the U.S. Environmental Protection Agency (EPA) classified formaldehyde as a probable human carcinogen under conditions of unusually high or prolonged exposure ..."
Dipping fish should cause neither unusually high nor prolonged exposure, whether in human or fish.