Paul... Excluding your years and years of experience.... you kind of boast about skipping some basic/easy maintenance steps in your tank.
I never said I didn't do water changes. I change water 4 or 5 times a year and always have. I have stated this many times on here and on my 9 year old thread about my tank.
I don't have test kits but I did for years. I also state that often. Occasionally I do let a LFS test my water but I know the readings as they are always the same as the tank is stable and I don't add anything that would change the parameters.
The fish are "usually" dying of old age because after keeping certain fish for many years I can figure out how long it is supposed to live and I know what fish look like when they are about to die of old age. I even put up a thread about this. My oldest fish now is a 23 year old fireclown, he will probably live 5 more years or so. My watchman gobies just died at about 12 years old, they spawned for all those years then just slowed down, stopped eating and faded away. I usually autopsy my fish and they were fine. Just dead. Not a single paracite, no liver, stomach or gill problems, no internal bleeding or tumors. Just old age and some fish only live a few years, fish like clown gobies. I had a breeding pair for a few years and the female just died. She was a few years old and I bought her as an adult. She spawned almost every week and covered my acropora with eggs. That can only happen for a few years as the fish gets used up.
To acquire a skill you just have to live long enough and keep fish for your entire life. I have had a fish tank every day of my life since I was about 5. I am now 65.
Even when I was in Viet Nam there was a tank home with an old catfish in it.
Anyways I am also a military man and have been taught about attention to detail and being proactive and not reactive.... so why not follow some simple maintenance steps.
My maintenance steps are vastly different from most modern aquarists. Did you see that video I posted above? I collect amphipods but more importantly mud for the bacteria. Almost no one does that because they are afraid of paracites, diseases or simply don't live near the sea. By adding bacteria I am by passing a huge problem that I feel is the bane of many tanks and the reason I don't have parameter problems. The bacteria eliminate those problems for me. If you never add bacteria from the sea, all you have is what was in the dealer's tank and his tank was probably medicated. I also feed live worms and clams every day. I only feed whole foods as I feel most of the nutrition in food is in the guts and not in the muscle such as shrimp tails or squid tenticles. This small thing keeps my fish in breeding condition so I don't have to quarantine as the fishes immune system
"always" protects them from diseases and paracites. Most people disagree with me on this but they "hardly" ever argue with me about it because I prove it works and has for many years. But it does take maintenance, just different maintenance than most people do. If your fish are not spawning or making spawning jestures, they are not very healthy as all fish spawn and do it all the time.