Like PYRU says, there's no one size fits all answer to water changes. There are too many variables, including but not limited to what and how you feed, filters and filter maintenance, plants or no and what type of plants, what your local water is like, and number or size of fish vs. tank size. Too many variables for someone to insist you must do this or can't do that. You don't want to skimp on water changes, but exactly how often and how much is something a good fishkeeper can best work out for their own tank and this may change over time as well.
As a former quite successful discus keeper I can tell you discus keeping also has many variables, there are different approaches and philosophies, including what to feed and what kind of tank to keep them in. Also, some strains are weaker than others. So, again, in the discus world some people insist on this or that, but a lot of it depends on the direction you go in keeping them. For example, you can increase or reduce how much water you need to change by what and how much you feed, size of tank compared to size and number of fish, and how you approach tank ecology. People become convinced of and insist on their way for various reasons, but there is more than one way and multiple reasons why more than one approach will work or why what works for one person doesn't work for another.
...As for 2" discus being so frail? Not when I kept them. If you find 2" discus to be so weak something is off what it should be, whether in the strain itself, something in how they were reared to that point, or something else going on. I never found 2" discus to be especially weak, not in my tanks.
I do agree on not having excessive current. Discus generally come from quiet waters. You do want good oxygen, but they are not fast water fish.
As a former quite successful discus keeper I can tell you discus keeping also has many variables, there are different approaches and philosophies, including what to feed and what kind of tank to keep them in. Also, some strains are weaker than others. So, again, in the discus world some people insist on this or that, but a lot of it depends on the direction you go in keeping them. For example, you can increase or reduce how much water you need to change by what and how much you feed, size of tank compared to size and number of fish, and how you approach tank ecology. People become convinced of and insist on their way for various reasons, but there is more than one way and multiple reasons why more than one approach will work or why what works for one person doesn't work for another.
...As for 2" discus being so frail? Not when I kept them. If you find 2" discus to be so weak something is off what it should be, whether in the strain itself, something in how they were reared to that point, or something else going on. I never found 2" discus to be especially weak, not in my tanks.
I do agree on not having excessive current. Discus generally come from quiet waters. You do want good oxygen, but they are not fast water fish.
