This is where things fall apart. It is absolutely impossible to fully recreate nature in a closed aquarium--by which I mean relying completely on "nature" to function as it does in the habitat. We use nature's methods (the naturally-occurring bacteria and so forth) but the ratio of fish to water is so incredibly different from any natural habitat, and there are the various natural processes that we cannot recreate naturally or artificially without water changes.
Your response reads like I'm not doing water changes, but I am???
This is why I called it a '
NEARLY Natural Habitat' and why
I do weekly water changes of 20-25%. I would likely agree with you completely if I did not do water changes. I quess the Walstad method succeeds without water changes because of a very careful match of low bio-load to a large plant mass, but balanced enough so that the bio-waste is large enough to feed the plants, I also wonder about the quality of food she fed her fish. Lower quality foods with grains as binder, then fishmeal result in far more fish waste than higher quality foods.
I honestly can't explain how the method succeeds (8-10 years!) without the mineral replacement that partial water changes would ensure, but apparently it can be done. perhaps with an additive like Equilibrium?
My tank nitrates continue to remain steady at around 10ppm and the water is crystal clear.
The "over-population" compared to natural habitats is so great it cannot possibly work. There is a limit to all of nature's methods. As an aside, the environment is able to "handle" short-term problems, such as CO2 emissions, but when these are maintained at such increasing levels for as long as has been the case, nature begins to break down, which is exactly what is happening today. Many believe we have already reached the point of no return. But the point is, that there is always that point, after which the natural system cannot function effectively and it slowly weakens and literally falls apart.
I do not know how you calculated your 50-75% WWC volume requirement? The research that I've done suggests that even a fish only tank can be well managed with much less than a 50% WWC.
Speaking of CO2, I failed to mention that in addition to the two filters (filled with bio-sponge) to filter and circulate water, I run a 9" streaming bubble bar on the left side 24/7. This creates a highly oxygenated environment with CO2 equalization.
The more fish in the tank, the greater the organics, obviously. Plants cannot hope to handle a fraction of this. And while the various bacteria do process the organics in various ways, the end product remains in the aquarium because the natural means of removing it is missing--and it is this part that the water change replaces. Consider that in the habitat the fish do not live in the exact same water for more than a second. The water they pull in through their gills is never the same water. You simply cannot achieve anywhere close to this in a closed aquarium unless you somehow have the water entering and leaving the aquarium 24/7 so it is always "new" or fresh water. Which brings me to the last paragraph.
Again, I'm doing weekly water changes.
I have considered a continuous fresh water flow in the form of a drip system and overflow, but my water issue (high source nitrates) has slowed me down. I may still if I can develop/leverage reliable long term inline nitrate filtration.
The massive dosing of chemical additives is not really necessary...adding some or perhaps all nutrients (in non-chemical forms, just to be clear, using natural nutrients) may or may not be necessary. The mineral content of the initial water, the amount of fish food added, and the number of fish and plants all factor into this. I have had planted tanks that received no nutrient supplements, even with my mineral-poor source water (GH is 7 ppm, or less than 1 dGH). But I also have a large tank where organics have been high (for mysterious reasons I have still not discovered) and the organic load has caused serious on-going problems. My point here is that increasing organics to this level that may indeed supply the plants' requirements (almost anyway), also brings on the problems for the fish and the biological system. Increased bacteria/diatoms (not the brown algae diatoms) causing hazy water permanently is only one manifestation.
I did not suggest 'massive dosing of chemical additives', I spoke of more massive water changes which removes too much of the organic nutrients and would likely require more chemical ferts to keep the plants happy. Again, I clearly stated that I would adjust the volume of water changes as necessary for balance. Again, and for years, I have had crystal clear water. But then in my efforts for lower nitrates, the tank was previously dosed with Stability and once long ago with Aquabella perhaps resulting in a very active substrate biology.
Perhaps you should consider dosing your problem tank with biological Aquabella or DrTim's Waste-Away or Eco-Balance, or better still might be Brightwell Aquatic's Microbacter7....as it sounds like there is a lacking of biology to properly handle waste?
