I think there is still much to learn about Crypto and other fish diseases. Who knows how many species, subspecies, mutations, etc. there are, and how much they differ from one another. If Crypto were a human affliction there would be financial incentive to find a cure or at least better treatments. By comparison, there's not much money to be made in the discovery of new fish meds. Which is why 30+ years later copper, a poison not an actual medicine, is still the #1 way we treat Crypto. With mixed results IMO. We also don't have a "Fish FDA" to monitor companies who put out "reef safe" Crypto meds, knowing full well they don't work. At least with humans the FDA requires scientific research/clinical trials before a med can be approved for sale. I wonder how it works with dogs & cats. Cause IME it's like the wild, wild west out there when it comes to fish medications.