What a lot of memories reading that brings back.
Yes, diseases in SW were not understood at all. Lots of bad information out there, just like today. Except today, you can get on here, and at least get some good answers. Durring this time I did find out that if your treated a tank with tetracycline the water would turn red in about 12 hours. I have no idea if this rendered the medication ineffective, or if this was just a color change. This color change doesn't occur in FW.
I started my first SW tank about 10 years earlier. It was a 20 long, so I had to stick with mostly smaller fish. At first, most of the fish were being collected from Florida and the Caribbean. SW fish from the Pacific were fairly rare and expensive. About 5 years later, there was a massive influx of Pacific fish, and at low prices. I found that most fish I bought at this time didn't live very long, even with good care. I believe that this was when collecting of fish using cyanide got going in a big way.
At that time, I also collected SW at Cape May. At one place it was easy park near the beach, and collect water. I always found it a little low in SG, and I had to let it settle out, but because it had at least some bacteria in it, a new tank didn't go through the usual bacteria bloom with slightly cloudy water.
It was really hard to find a LFS that even carried SW fish back then. I'd hear from others about how a store did carry SW fish. I'd visit the store and find that the either never did or got out of that. That's where I became willing to travel long distances to obtain SW livestock.
Thanks for posting!