Here’s the thing - ponds come in different types, the two main categories being dedicated koi pond and eco style garden pond.
A DKP - which is what most koi enthusiasts will promote - has issues that are unique. For instance, they tend to be slightly overstocked, or the fish they purchase are somewhat expensive. So their pond goals are very different than those of us who are keeping eco style garden ponds.
My pond, the fish, the plants, the water the wildlife are all equally important. So I make decisions based on what is best for the entire ecosystem that I am trying to maintain. A dedicated Koi pond keeper would never put gravel in a pond for example. In fact, they would never rock a pond. In my earlier years of ponding, the preponderance of information available on the Internet was directly related to dedicated Koi pond keepers. I am grateful we have a forum which allows us to share about different ponding styles.
Having said that it’s important for you to understand that the reason why salt “works” for koi is because it literally irritates their skin which increases the slime coat. A more robust slime coat makes it more difficult for parasites and bacteria to attack the fish. It’s not an accusation to point that out - it’s simply a biological fact. You say your fish look “happy“ - that’s positive. We all know what you mean when you say you observe your fish and you like what you see. We all do the same thing - observation is our greatest tool.
However, just like overusing antibiotics, eventually the things that you are trying to prevent or kill will find a way around it. That’s nature.
