Q: Malachite Green and Formalin in planted tank

Greetings all,

Well, call me an idiot, but I made the mistake of adding a couple of
fish from a local store (one that has good reputation, runs UV
sterilizers, etc) to my main tank without quarantining them, and guess
what? Correct, you get a gold star!

An outbreak of Ichthyophthiris - after 2 years of being completely
free of the organism. Arrgghh....

What I want to know is if Malachite Green and Formalin will harm the
plants in a 75 gal planted tank, dosed at 1 drop per gallon.

I don't have a tank big enough to hold all the fish independently for
treatment, and am hoping to treat the main tank instead.

Just call me stupid,
Greg