You have not indicated in what way my fish are not healthy. You have postulated that there's "only one way to achievee [sic] clean water and healthy fish, and that is regular substantial water changes". I disagree, and I think my tank proves the point. Give me a metric on a different way to measure fish health, and I will be happy to discuss; but until then my metric of normal and vigorous feeding, and general happy fish motion; indicates healthy fish. I am sorry that it the data does not fit your theory, but science is data driven.
Metalhead88 is bang on. But as you have asked how I know, I will do my best to answer.
This is a scientific hobby, totally. We are keeping living creatures within an environment that is as complex as any on this planet because it is totally aquatic. We must keep them in an aquatic environment and that immediately presents us with limitations and natural laws of chemistry and biology that will play out no matter what we do. We must research these and understand them, and accept that we cannot possibly change them, because they are crucial to the health and life of the fish, the bacteria, the invertebrates, the plants. These living organisms have evolved over thousands if not millions of years to function the way they do, in very specific environments that are crucial to the functioining of their physiology and metabolism. If any aquarist wants success, he/she must recognize this and accept it.
We learn how by listening to the experts. When I get sick I go to a qualified doctor for advice. I have the option of accepting it or ignoring it, but I am making a huge mistake if I do the latter without scientific evidence, for example the reasoned advice of an equally qualified doctor. There are biologists, microbiologists, and ichthyologists that have spent years studying their field, and contributing knowledge. We can easily know who they are, their credentials speak for themselves.
No aquarist can possibly say their fish are "happy" because you cannot talk to them. It is much easier to recognize happiness in mammals like dogs, but that does not happen with fish. We can however research what the fish species needs and requires and
expects, and then provide that environment as close as we can. If we do this, then we can assume the fish will probably be in good health, and more likely "happy." Thinking that just because the fish is swimming and eating and spawning it is "happy" only shows that one does not even begin to understand the fish. Like all animals, fish have an inherent will to survive, and they will make every effort to do so no matter what obstacles we throw at them. Externally they may very likely appear no different, until they die either prematurely or from some disease they should have been able to handle except that we deliberately made their life difficult by not recognizing their needs and providing for them. And by understanding their internal life processes and ensuring those are possible without hindrance.
