I did a search and found out one of the ingredients is malachite green (which, like you said, will stain the silicone seals in a glass tank). I have used a medicine with malachite green in an acrylic "critter keeper" with no staining. I've also used methylene blue in an All-Glass brand acrylic aquarium (2.5 gallon bowfront) and that tank didn't stain either. That water was so dark blue that I could barely see the fish, but there was no staining to the acrylic.