It’s not about captive bred fish... it’s about wiping out only 90% of a disease leaves the hardiest most resistant parasites alive. Kind of like people who don’t take the full course of antibiotics you’re only encouraging the rise of highly resistant diseases.I don't think the cichlid comparison is really relevant to the saltwater hobby. All you need to breed them is a tank to put the babies in. This consistent over the course of years breeding of cichlids with mostly very relaxed to non-existent quarantine and disease management is what led to the bloat building a resistance by the same strain being exposed to treatment over the course of many generations. That is never going to happen in the saltwater hobby at least not in that scale, Most captive bred saltwater fish have to be bred in a lab grade environment with very strict prevention and disease/parasite management/eradication procedures to be successful. Even clownfish arguably one of the easiest to breed when done commercially still have these procedures. We will always find different strains of ich/brook/velvet etc, that are more/less resistant to various treatments simply because the ocean is vast and new organisms and variations of organisms are discovered every day. Prophylactic treatment and proper quarantine Should be the gold standard aspired too for any serious hobbyist, Allowing these parasites/diseases into your system will put you one stress event away from many more fish fatalities than you would have had otherwise. There's a youtube aquarium channel where the person that makes videos and gives advice has killed alot of expensive fish with ich, once I could forgive but they didn't learn and did it more times, and is still doing it. I often wonder how many more fish he has killed with his viewers following his example...