Plants can grow without injected CO2 and added ferts.
Plants can't grow without injected CO2 and added ferts.
I think we have to start by agreeing those two statements are true, since we've failed to say which plants we're talking about.
@anewbie grows the plants I do, apparently about as I do. Good plants, but easier ones. Others grow plants I can't, and since plants aren't my priority, that's fine by me. But we have to accept both statements.
Similar things can be said about fish. The diversity of life means a diversity of needs, specializations and abilities to adapt to changes. "Fish" isn't a very informative word, any more than "plant".
Everyone here is doing something wildly unnatural. We make glass boxes that we place in isolation in air environments, and we keep aquatic life in them. We try to recreate natural processes that occur in waterways millions of times larger than those boxes. I have 45 tanks in what is a large fishroom for the hobby, and my total water volume is less than a cut off pond beside a dry season brook.
So I change water to try to emulate a natural turnover. I fail, because thousands of litres move through a brook every hour. But I get close enough that my fish can breed, and thrive with long lifespans and behaviour not unlike what I've seen in nature.
Others use plants, and try to absorb the inevitable pollution of a tiny water body. If they are meticulous, that too fails in a workable manner, and creates something very beautiful while operating as well as it does. It can be good enough.
We use technology. CO2. DIY hacks. Creativity. Inventiveness.
We even have people who develop faith in crazy theories and do nothing positive, a la father fish, trying to use wishes to make the world simpler than it is. Magic is a popular tool.
I think we have to call out the latter group, as they do active harm. But all of our fiddling, attempting, inventing - all of it can come from a sound scientific basis as we try to achieve a very weird dream. There's no one road.
We're a forum here, and there are many new aquarists who check in. So whatever we do we have to try to be clear about why. I have a friend who has taken up quilt making, and she works on technique as a matter of basic sense. Yet we have people who don't want to work on technique in fishkeeping, as if it were something different as a learning curve. I'll argue for water changes, but if an aquarist finds a different way to achieve temporary balances and can provide proof, I'll listen. Since it takes skill to pull off those techniques, I won't suggest them to newcomers.
Learn to work with water. Learn to define what your fish are, what your desired plants are what their natural history obliges you to do. Then, if you get fancy and learn to work with water chemistry (beyond the useful toy API kit) , develop and share a system. It will be different from what others do, but the goal's the same.
And roots also clean the substrate and keep it healthy.
