Back in the 1950s when I started keeping fish, this concept was called a "balanced aquarium", and seemed achievable, within limits.
But the balance of plants to animals was the key.
It would work with 2 guppies in a 20 ga tank with 20+ thriving Vallisneria plants, or 1 Betta in a 55 with 60 water sprite plants (low fish to plant ratio).
Then again these were the average type fish people kept back then. But....
Then larger aquariums came into vogue and built, and larger fish like cichlids started being imported.
An equivalent tank for a single oscar (to the above "balanced" small ones) might be 1 oscar in a 500 gal tank with a veritable garden wall growing from it.
As many of these larger fish becoming available, they also needed more specific conditions and required more and more advanced equipment to simulate nature like pumps to replicate stronger flow, or high oxygen content, and narrower precise water parameters, as opposed to simple air stones..
Where a Betta can live well in a low oxygen, high nitrate environment, a Denizen barb or Geophagus sveni may not last even one night.
I am trying to achieve this with my 180 gal tank, with its heavily planted 125 sump refugium, yet still, frequent water changes are needed to keep water parameters within the range these fish require. (such as an undetectable nitrate level like the water they were caught in)
The only equipment I use is a 1500 GPH pump and a couple powerheads to simulate riverine flow and conditions.
The 300 gal system is stocked with only 8 (no larger than 8") fish, the planted refugium is placed in heavy sunlight to encourage vibrant plant growth, and has a dozen mangrove saplings, and has an open open to make use of rain, and allow terrestrials room to grow.
The refugium also uses a cadre of about a dozen or more shrimp to help break down excess metabolites into more usable food for the plants
The tank above, the sump/refugium below
The mangroves below
