*****if Formalin, malachite green, and kanamycin sulfate are compatible with each other or if they will adversly effect my
While I agree that mixing medications is not a good fishkeeping practice, I think I can confidently say the medications can be mixed together.
Formalin is a preservative, and is used mainly to combat ich. I'm not sure exactly its action, but believe it is distinct from the other two. Malachite green is a protein-binding dye. It's mechanism of actiion is binding to the surface proteins of the bacteria, which reduces the bacteria's viability -- it may be killed or weakened and reproduce slower giving the immune system more time to combat the bacteria. Kanamycin sulfate is an antibiotic. I think it inhibite protein synthesis by binding to the ribosomes of the bacteria.
The straight answer to your question (and *not* commenting on fish husbandry practices) is that the medicines are compatible because each has a different mechanism of action. There will be no "additive" effects.
The only proviso is that the kanamycin may be somewhat less effective if the malachite green binds to whatever protein/pore through which kanamycin is imported into the cell. But psysiologically speaking (or perhaps more importantly biochemically speaking, their effects are not additive.)
PS: I wouldn't want to be the biological filter in that tank right now!!!
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