malachite green

In 1992 Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk.

Malachite green can also directly stain endospores within cells; here a safranin counterstain is often used.

R. Trebino and A. E. Siegman, "Subpicosecond relaxation study of malachite green using a three-laser frequency domain technique," J. Chem.

Thus treatment with salt (or with freshwater for marine fish), formalin, quaternary ammonium compounds, malachite green, and antibiotics for example can be given at high dose for short duration, making them more effective against the disease organisms while offering a better safety margin to the fish through shorter contact time.