Jay,
The large majority of public aquariums use all sorts of methods not available to the public. The idea that one size fits all is why there is so much abrasion between the always prophylactic crowd and those who have not had the same success and use other methods. I am more than a little tired at the 'my way is the only way attitude' that you and spare time exude every time you show up. I respect your advice and have sought it out even recently for the health of a long term resident of my little aquarium. That said, the biosecurity you mention goes right out the window at the many Coastal aquariums that use a pump and dump method for filtration in their systems. The only filtration of the incoming water is sand filtration, U.V. and temperature adjustment. Now convince me that there is no possibility of some parasites slipping in with the fresh saltwater supply. So even thought the fish have experienced prophylactic treatment they are subjected to possibly being exposed through the water supply. Now maybe the cold water acts as another line of biosecurity on the incoming water. Again this is not possible for the hobbiest on the same scale.
How about access to diagnostics that the average hobbiest does not have? Proper treatment demands proper diagnosis. If you as a person were exposed to biosecurity by health care professionals you would surely die after a course of preventative treatment that was not indicated by proper diagnosis. It is akin to being given chemotherapy when no cancer exists. Your prognosis will not be good. Most preventative medicine is around holistic methods that work in harmony with the body to reduce the incident of disease. These include proper diet, exercise, freshwater and air, and mental health. These are indeed preventative and successful. If you believe in evolution or creation, then you must accent to this being part of the commonality of all creatures and their healthy lives.
Many of us with long term success have been unable to successfully implement prophylactic treatment without higher loss rates in the population of fish we care for. As a result we found ways that are more holistic and work with the fishes own protective mechanisms for our success. It has worked for many and it is not lazy. It requires observation of what a healthy fish looks like so that you can recognize abnormal patterns in an unhealthy fish at the purchase level. I have seen many unhealthy fish in public aquariums in various places around the world. Is that an indictment of public aquariums? No it is not, it is just a much larger scale than the hobbiest aquarium. Your experience is shaped by the requirements of your previous employment and you must admit to a bias as a result of that experience. I admit to a bias as the result of my experience. In many ways we cannot understand that the world's oceans are teaming with life where no biosecurity exists and yet they thrive and some die. But for the most part they thrive in natural conditions and the large majority have stable populations. Some of us want to more closely follow what we observe in nature and that gave rise to the reef hobby. Fish in the wild live and die everyday. It is a fact that is beyond human control. We live and die everyday and that is a fact beyond human control. It is part of the rhythm of life and some of us prefer to learn how to adapt to that rhythm for best results. It is never lazy and requires lots of attention. Given the chance we could learn from each other in these diverse camps of experience.