This is of course true as proven by all the disease threads. I don't, and never have believed in a disease free tank of any type. Fish diseases, for me are a non issue because rather than trying to eliminate diseases and parasites, I embrace them and welcome them in my tank. I just keep my fish immune so I don't have to worry about any of this stuff. My tank and fish have been living alongside parasites and diseases for over forty years. It just seems much easier and I never once, in all those years had any fish come down with a communicable disease. All the paired fish are spawning and living long enough to die of old age which is all I can expect. I have been hearing that playing Russian Roulette thing for decades now and it is true that my tank may crash from disease some day. But in less than 4 years my tank will be 50 years old so it has had quite a good run of health. If it crashes now, I will still call it a success.
It seems to me that it is much easier to keep the fish healthy and immune with no quarantine tank, hospital tank or medications than to go through all of this work. We all "enjoy" our hobby in different ways, I prefer not to have to worry if I am introducing a disease and to just sit in front of my tank to enjoy the view. I know there will be no spots or torn fins on a fish because there never is. I am going to buy a new fish tomorrow because one of my spawning yellow wrasses jumped out. I will acclimate it for 20 minutes or so and put it in my tank knowing he will be fine. Unfortunately very healthy fish can jump higher than marginally healthy fish so I do lose some like that.

Healthy fish are spawning fish. If they are the type of fish that will spawn in a tank, no manta rays.
Crashjack. 14 acres in my town would cost well over $40,000,000.00. Your dogs are really lucky and I am sure they appreciate you for that.