My Theory on no water change Aquariums

Just Letting you know I'm not an English major.

There are a lot of theories on no water change aquariums and how to do them but here's my general interpretation and how to execute it.
One note is one of the biggest things that people are worried about is algae but if you are truly worried about the fish, you'd know it isn't unhealthy for them it's just unsettling to the eye. Now with that out of the way let us get into it.

The nitrogen cycle is how we all know it going from Ammonia to Nitrite and finally to Nitrate. There isn't too much to how to start it just introducing some form of Ammonia and maybe some beneficial bacteria to it (only if you want to add the bottled bacteria) BUT NOT FISH. On that it's just how people say it set up your tank and LEAVE IT ALONE, at least for six weeks regularly testing to allow bacteria to colonize properly. Now with that out of the way let's get advanced.

Everyone is scared of excess nutrients and trace minerals in an aquarium but in my experience it's nothing to worry about it just gives the plants and invertebrates more room to grow. What I mean by that with invertebrates is that shrimp and snails need certain minerals to grow and reproduce. And yes, snails or shrimp are necessary in this theory. If the nutrients aren't there or are in minimal amount you won't be able to have them grow their exoskeleton or shell and possibly, they can die from this.
When people do water changes it removes a lot of their essential nutrients and with this comes less healthy for shrimp and snails. If this happens there won't be a beneficial breeding colony as some shrimp and snail species do die off quickly. So, in the long term you could lose your whole cleanup crew that doesn't produce a large bio load. And that leads to my next thing which is your bio load.

Shrimp and snails compared to fish don't produce a large bio load, so you have to be sparce with your fish. This means the one inch to one gallon theory must be followed to the letter. If not, you could possibly have major crashes in your aquarium.

The next thing I want to talk about is the lighting and filter. From my experience and what I've seen you should try and have lighting that isn't too strong. I would say that the best lighting would be an easy to medium light intensity. This allows your plants to grow well without having too much algae building up as too much algae may lead to leaves of plants being covered and dying. So, what I said earlier about algae does have a limit.
Next, we'll move on to filtration. You really don't need much. Filtration is a tricky thing and can do different things in your aquarium. But what I'm most worried about is filtering out big contaminates and having a place for some ammonia filtration as I believe it is beneficial.
If you want more information on that there are plenty of articles on it on the internet, but I do want to state one thing. DON'T BUY INTO THIS CARTRIDGE AND NEEDING TO BUY NEW ONES EVERY WEEK THING. Another thing is If it works LEAVE IT. Don't be that person who wants to improve something because they think it's better than what is going on. If you do that it's a 50/50 that your fish or shrimp will die (in my experience).

Now this my final thing (sorry if this post is long). Floating plants are one of the bases of this theory. They basically do a water change for you. From what I've seen and read as long as you have a fast growing or average growing floating plant you will be fine as long as you remove them when they start getting in excess. Some fast-growing floating plants absorb excess nutrients algae would take advantage of and by removing them when they are in excess (floating plants) you are removing the excess nutrients and allowing the floating plants to grow back.

Anyways this is my first post so sorry if it isn't the best and I know it didn't cover everything in detail (mainly because every fish and plant needs different parameters) but I hope to see the comments anyways peace.

 

Lots of good stuff here! But also some issues that at the least need more elaboration. I'll touch on one-- the comment on nutrients (minerals) and invertebrate exoskeletons. Basically, I think this area is far too dependent on individual tap water parameters and tank setups to be able to make all-size-fits-one comments about.

I would love for my tank to be a low water change tank, and in fact specifically designed it to try to achieve this goal.

But my tank devours gh and esp. kh. As far as I can tell, my plants are basically using up the calcium and other minerals in my high gh l/medium kh water. Which means that I wind up with dangerously low kh values (3-4 degrees) if I consistently go more than a week or so without water changes for both my shrimp and endlers, as evidenced by decaying shell quality on snails. So as currently setup, I don't believe my tank can be a low or no water change tank without inhabitant losses

Perhaps with higher kh from the tap and/or different plants things would be different. So while I think there may be conditions under which the above is correct for nutrients/minerals, I would caution that there are other circumstances in which they may not be and water changes beneficial.

In any event, a very intriguing post--thanks for posting/starting the conversation!

 

It's no problem and I'm not going to lie I'm no fish expert, but I plan to start a tank soon and I want to take that tank as a constant post. With that I want to take the tank and have a post where I start going over specifics of what I learn in detail about this. But I didn't want to be too specific about this for one reason and that's because every fish, plant, and tank is different, and I want people to do their own research into their fish so they can find what's best and the information you gave me is very helpful. Thank You!

 

Can you please do an edit of the post and break up the wall of text into smaller paragraphs along topic lines? Right now it's really hard to read, because you switch subtopics very often. I had to give up after not even half of it. I'm used to my students doing that all the time, but this here isn't my workplace.

 

Can you please do an edit of the post and break up the wall of text into smaller paragraphs along topic lines? Right now it's really hard to read, because you switch subtopics very often. I had to give up after not even half of it. I'm used to my students doing that all the time, but this here isn't my workplace.

I just changed it. Thanks for the advice! I hope it is easier to read for you and while it still is a little everywhere all main topics are separated now.

 

Thank you very much!

So in short almost the classic approach:
Low stocking density, great mass of fast growing plants.

But: The full spectrum of nutrients have to be available in a cycling fashion of growth, death and decomposition. Light and filtration are irrelevant. That makes for a low maintenance - almost - no waterchange tank.

There are several flaws, though:

When people do water changes it removes a lot of their essential nutrients and with this comes less healthy for shrimp and snails. If this happens there won't be a beneficial breeding colony as some shrimp and snail species do die off quickly. So, in the long term you could lose your whole cleanup crew that doesn't produce a large bio load. And that leads to my next thing which is your bio load.

If you have soft water the demand for minerals used by plants, invertebrates and ultimately the microorganisms in the filter may very easily exceed the supply. In those cases waterchanges replenish the trace elements and minerals. Yes, they may remove and dilute Nitrates and other organic compounds, but there has to be a source of non-organic nutrients or the organisms that bind them have to have short livespans and be left in the tank to decompose, so the stuff stays in the cycle. (No, not the nitrogen cycle, there are more.)

Shrimp and snails compared to fish don't produce a large bio load, so you have to be sparce with your fish. This means the one inch to one gallon theory must be followed to the letter. If not, you could possibly have major crashes in your aquarium.

Erm... no. It just ends you up with a die off in plants and that's it. The inch per gallon-rule is massively outdated.

DON'T BUY INTO THIS CARTRIDGE AND NEEDING TO BUY NEW ONES EVERY WEEK THING.

Had bad experience? This is well known in the hobby. You could rather say: Don't buy into marketing in general.

Another thing is If it works LEAVE IT. Don't be that person who wants to improve something because they think it's better than what is going on. If you do that it's a 50/50 that your fish or shrimp will die (in my experience).

Yeah... well... common knowledge as well.

Floating plants are one of the bases of this theory. They basically do a water change for you. From what I've seen and read as long as you have a fast growing or average growing floating plant you will be fine as long as you remove them when they start getting in excess. Some fast-growing floating plants absorb excess nutrients algae would take advantage of and by removing them when they are in excess (floating plants) you are removing the excess nutrients and allowing the floating plants to grow back.

As said above: The plants also use and bind anorganic nutrients and minerals in their tissue. You remove the plants, you remove these nutrients permanently.

Another thing that makes no-waterchange-concepts problematic: Build-up of non-essential waste products like DOC (dissolved organic carbon, a measure of organic compounds dissolved in the water) may still tip the scales of a carefully balanced tank easily.

Your approach is halfway towards a Walstad or a low tech planted tank, maybe also towards certain biotopes. You also didn't address the problem of evaporation at all.

A no-waterchange-tank is not as desireable as you might think, just as the famed/infamous no-NO3-tank.

Some correct assumptions are made, I have to say though: Back to the drawing board.

 

It is a theory, and your knowledge has helped me a lot and honestly will help me in the future. I will go back to the drawing board because I do want to find a way to actually do a no water change aquarium completely kind of like biotope jar almost. It will be a while, but your knowledge has helped me quite a bit. Also, I want to find a way to naturally put water back in an aquarium and if I can make a product that can eliminate top ups. I may be on to something with that, but I'll have to do some research. And I do want to find a way that requires literally nothing but plug and play unlimited top up one day.

 

It is a theory, and your knowledge has helped me a lot and honestly will help me in the future.

You're welcome.

And I do want to find a way that requires literally nothing but plug and play unlimited top up one day.

I'll be blunt here: People have tried for decades to get there. Still nobody has reached that level and every time somebody made that claim they lied. Knowingly or un-knowingly. The laws of nature and physics don't allow for this, sadly. You can realistically reach a close approximation (Which I honestly wish you to achieve!), but the real deal is as achievable as a perpetuum mobile.

 

There's no such thing as a "no water change" aquarium. Reason being you have to replicate everything in nature and guess what? Water changes are a fact of life in nature. whether nature does it or you do it, water depletes and gets replenished in a never ending cycle, new nutrients are moved in, Old stuff is carried off, if it doesn't function it crashes. Same way a lake can go dead given the right conditions.

That's not to say you can't get close to it, or do things on such a minimalist and balanced scale that it takes forever before a water change needs to happen, and are simulating rainfall with top offs of rainwater ( can't use tap water it will mess up the balance without water changes).
Ground water if full of minerals and nutrients, that creates the bodies of water, rain maintains the balance, or tidal flows, or currents, ect. Compensating for evaporation.

You can build towards a long time between water changes, any misstep will crash it but if you're lucky it will just go out of balance and vex you instead to figure out how to get it back in balance.
It will eventually crash itself also. Plenty of tanks can handle a plant dying off and rotting away, not so with a dead fish, dead snails ect. And it would need to be able to handle that also which is where water volume comes into play and a fish tank just doesn't cut it. Dead animals, even shrimp and snails create a big bioload.

In theory it all sounds plausible, in practice it's all incredibly difficult to retain a balance without stuff leaving the aquarium and entering the aquarium, it's just how it works in nature and when it doesn't work it becomes a dead stagnant pool of water.
What gets overlooked is water keeping in nature is done on a macro scale and in aquarium keeping its done on a nano scale, even large aquariums.

I won't talk you out of trying, I will say it's been tried, I've tried many things except plants, and I've gone long periods of time without water changes, however the end result is always the same a crash.

That said, I did nothing but top off for 5 years doing nothing special at all and no plants, KH 0, GH in the 400s, pH below 6.0, no ammonia or Nitrites, and Nitrates in the 500+ range.

The fish that were there all lived, two kissing gouramis lived to 15 years old through that.
I couldn't add new fish to it without them dying but the ones I had in there that slowly adjusted to it lived just fine.
So in that respect, it was a no water change tank that worked at least until I realized I wanted to get new fish and had to get it back to "right".

I could have likely carried on just topping off and not water changing for another 5-10 years as the fish died of old age. Doesn't mean it's right or in balance even though it's working for the stock, the fish never reproduced, I didn't and couldn't have plants without them melting and dying off also.
I don't claim I had a no water change tank, I claim I had Old Tank Syndrome which is the accurate term for it. But I could have passed it off as no water change for 5 years to people and everything is fine as long as we all don't look at my water parameters, not even algae would grow the tank always looked pristine.
Now that I have it back in order, I'm getting algae again and fin fungus on fish.. but I can keep new fish in there now!

No water changes can happen and it can work for the fish kept a long time, it's just smoke and mirrors though, anyone doing it either has a ton of plants and very low stocking, or isn't being honest about the water parameters.

You'd seriously never know this tank, at the time of this picture KH 0, GH in the 400s, pH below 6.0, no ammonia or Nitrites, and Nitrates in the 500+ range,and like that for months and months.
I could show you tests of my tapwater and claim I found the secret to no water changes, show the filter and no special attachments, the clean looking tank, healthy looking fish.... it would be a hoax though but how would people on the internet know? just saying. I could tell any story I like about it, I wasn't doing water changes, but it was far from healthy, but nobody else needs to know that.


I just found a youtube video from 6 years ago of a guy pushing 3 stage "trickle filters" as some new tech, saying it would run zero nitrates on a tank..... NOPE. Not how they work at all.
heck, send me some free equipment and I'll tell yall it's wonderful!!!! hahahaha

and that's where I think a lot of this "zero water changes" thing comes from, sales pitches. Possible to do it, sure, employing various methods and some luck and low low stocking, you can get there. Some magic plenum or a 3 stage trickle filter, or some costly biomedia,,,,, nope. the old too good to be true line is at play and it's usually someone selling something in the end.

 

There's no such thing as a "no water change" aquarium. Reason being you have to replicate everything in nature and guess what? Water changes are a fact of life in nature. whether nature does it or you do it, water depletes and gets replenished in a never ending cycle, new nutrients are moved in, Old stuff is carried off, if it doesn't function it crashes. Same way a lake can go dead given the right conditions.

That's not to say you can't get close to it, or do things on such a minimalist and balanced scale that it takes forever before a water change needs to happen, and are simulating rainfall with top offs of rainwater ( can't use tap water it will mess up the balance without water changes).
.

I think this gets at the heart of things --a truly healthy, eternally-lasting no water change tank is not usually realistic because it represents the reverse of nature.

I will add that at the very extreme, I am not entirely sure that the above comments about the impossibility of a no-water-change tank are technically correct. Could one maintain healthy water parameters for a decade+ in a 1000 gallon tank with 3 male endlers, substrate pre-tailored to buffer kh, floating plants, rainwater topoffs and food tailored to provide nutrients for the plants? Perhaps?

But this in turn really points back to a takeaway of the above comment--that in large part this is all a matter of scale. I.e. at some point, the difference between a pond and a tank is more hazy than clear cut.

My grandparents had a small farmpond without a continuous inlet or outlet; the only addition of water was run-off and rainfall. Water left via evaporation. The pond probably held 40,000 gallons. Obviously you could have drained the water from the pond and put up a four glass walls and a glass bottom in the pit to make a tank and have attained the same effect. They didn't have fish in there, but I am sure they could have stocked it with bluegill at the least if they had wanted.

So by messing with scale (there is little difference between 3 endlers in a 1000 gallon tank and 10 largemouth bass and 50 bluegills in a hypothetical 40,000 gallon pond), and putting in the work to add water, pre-prepare substrate, etc., I suspect we could functionally attain a no water change tank that lasts a decade or more. But, of course, no one really wants a 500-1000 gallon tank with only three male endlers.

So in practice, the eternal (or at least decade+) no water change, healthy tank likewise seems to me to be a goal not worth chasing for most. (even though I won't rule it out completely, in part because of what some such as LRB Aquatics seem to be able to do)

 

I’d check out diana walstad’s book on it, she is a scientist, not a salesman. And she tries to explain to non-scientists how to do a no water change tank, but she definitely encourages top-offs. I have not read it yet, on my long list of books to read. It’s called "The Ecology of the Planted Aquarium," by Diana Walstad. She’s kind of revered in the hobby.

I see a lot of non-plant keepers posting on here, and honestly, without plants or at least a ton of algae, this couldn’t work. I personally have a fully stocked tank FILLED with valisneria, and I only have to do wc once a month. Besides top offs. But I’m sure it could be prolonged if I had a smaller stock and edited other components too.

 

. . . My grandparents had a small farmpond without a continuous inlet or outlet; the only addition of water was run-off and rainfall. Water left via evaporation. The pond probably held 40,000 gallons. Obviously you could have drained the water from the pond and put up a four glass walls and a glass bottom in the pit to make a tank and have attained the same effect. They didn't have fish in there, but I am sure they could have stocked it with bluegill at the least if they had wanted.

So by messing with scale (there is little difference between 3 endlers in a 1000 gallon tank and 10 largemouth bass and 50 bluegills in a hypothetical 40,000 gallon pond), and putting in the work to add water, pre-prepare substrate, etc., I suspect we could functionally attain a no water change tank that lasts a decade or more. But, of course, no one really wants a 500-1000 gallon tank with only three male endlers.

So in practice, the eternal (or at least decade+) no water change, healthy tank likewise seems to me to be a goal not worth chasing for most. (even though I won't rule it out completely, in part because of what some such LRB Aquatics seem to be able to do)

If it had been there for any length of time I would be very surprised if it didn't have some kind of fish in it, and bluegill would have been a good candidate. I have often seen relatively small bodies of water, located where they couldn't get any fish washed in from another body of water, have perch in them.

I don't have any scientific basis for this, but my best guess is that the eggs are carried from one body of water to another on the legs of wading birds.

 

I’d check out diana walstad’s book on it, she is a scientist, not a salesman. And she tries to explain to non-scientists how to do a no water change tank, but she definitely encourages top-offs. I have not read it yet, on my long list of books to read. It’s called "The Ecology of the Planted Aquarium," by Diana Walstad. She’s kind of revered in the hobby.

I see a lot of non-plant keepers posting on here, and honestly, without plants or at least a ton of algae, this couldn’t work. I personally have a fully stocked tank FILLED with valisneria, and I only have to do wc once a month. Besides top offs. But I’m sure it could be prolonged if I had a smaller stock and edited other components too.

But I think the thread is about a true no-water-change set-up, as opposed to a 'few water change' setup? I don't think anyone is disagreeing with the possibility of going weeks or months between water changes. The question being considered, I think, is whether this can be extended to years without detriment to the inhabitants and health of the ecosystem.

I will also add that I have a planted tank that does not seem to be able to go weeks without a W/C easily. In fact, I am still confused as to why others don't run into the problems with mineral deficiency that I do--I may start a separate thread about this someday!

 

I’d check out diana walstad’s book on it, she is a scientist, not a salesman. And she tries to explain to non-scientists how to do a no water change tank, but she definitely encourages top-offs. I have not read it yet, on my long list of books to read. It’s called "The Ecology of the Planted Aquarium," by Diana Walstad. She’s kind of revered in the hobby.

Yeah, there's one problem: As far as I know Mrs. Walstad has paddled back on several of her points and revised the book. So best get the newest edition and make sure to look into her commentary.

 

I am actually arguing they can go for years without a waterchange. Though I would also say that it depends on what type of water you have, I would argue well water is better for the long term than city water, as top-offs replenish the minerals.

 

Though I would also say that it depends on what type of water you have, I would argue well water is better for the long term than city water, as top-offs replenish the minerals.

The source is irrelevant. Top-offs with too mineral rich water only make said minerals build up and up and up. That's how many people even with moderately soft water end up with incredibly high GH and KH levels when only topping off. There are dozens of cases here on the forum that went exactly like that.
The problem is evaporation removes only water. everything in it is left behind.

 

I think this gets at the heart of things --a truly healthy, eternally-lasting no water change tank is not usually realistic because it represents the reverse of nature.

I will add that at the very extreme, I am not entirely sure that the above comments about the impossibility of a no-water-change tank are technically correct. Could one maintain healthy water parameters for a decade+ in a 1000 gallon tank with 3 male endlers, substrate pre-tailored to buffer kh, floating plants, rainwater topoffs and food tailored to provide nutrients for the plants? Perhaps?

But this in turn really points back to a takeaway of the above comment--that in large part this is all a matter of scale. I.e. at some point, the difference between a pond and a tank is more hazy than clear cut.

My grandparents had a small farmpond without a continuous inlet or outlet; the only addition of water was run-off and rainfall. Water left via evaporation. The pond probably held 40,000 gallons. Obviously you could have drained the water from the pond and put up a four glass walls and a glass bottom in the pit to make a tank and have attained the same effect. They didn't have fish in there, but I am sure they could have stocked it with bluegill at the least if they had wanted.

So by messing with scale (there is little difference between 3 endlers in a 1000 gallon tank and 10 largemouth bass and 50 bluegills in a hypothetical 40,000 gallon pond), and putting in the work to add water, pre-prepare substrate, etc., I suspect we could functionally attain a no water change tank that lasts a decade or more. But, of course, no one really wants a 500-1000 gallon tank with only three male endlers.

So in practice, the eternal (or at least decade+) no water change, healthy tank likewise seems to me to be a goal not worth chasing for most. (even though I won't rule it out completely, in part because of what some such LRB Aquatics seem to be able to do)

But this is kind of what I mean, the farm pond has evaporation to contend with, if there isn't rainfall, then the water continues to condense, maybe farm use drops the level further and further also to water plants or cows. maybe it drops to a certain point and ground water seeps upward maintaining the level also at a baseline. Maybe if you put up the 4 walls of that 40K gallon tank, in a decade or two, you get enough buildup and mud on the bottom to get a similar substrate to the bottom of the pond, that has aerobic and anaerobic bacteria, that the water then runs all cycles and can support life, but that pond or tank is still a cold snap or a heat wave or a drought away from a bloom and bust and rebirth or,,, a dead pond.

Here in South Florida, with the canals and water retention ponds, when it gets pretty cold, we get non-native fish die offs, Hundreds of dead fish doing the backstroke, stinking up the place, summer rolls around and natives survived, and some non-natives that happened into the right place at the right time survived. in a pond or canal, all that death is still quite devastating, but survival of the fittest. Meanwhile, in a tank, something like that is a tank killer.... unless you have that 500 or 1000 gallons and 3 endlers. (a bit extreme but yeah, you need a ton of water and a low amount of fish.)

Also in that pond you'd need to factor minnows for the bluegill to eat, and you need to factor that the bass are going to eat the bluegills. there's a whole set of processes functioning in nature that are difficult to reproduce and maintain in an aquarium. you need the mulm, the algae, the mud, the diatoms, the "critters" the death and the rebirths. for it all to be self sustaining and self replenishing..... as long as the rains keep coming of course, or, you just have a hole of water and nothing beyond bacteria and insects.

I’d check out diana walstad’s book on it, she is a scientist, not a salesman. And she tries to explain to non-scientists how to do a no water change tank, but she definitely encourages top-offs. I have not read it yet, on my long list of books to read. It’s called "The Ecology of the Planted Aquarium," by Diana Walstad. She’s kind of revered in the hobby.

I see a lot of non-plant keepers posting on here, and honestly, without plants or at least a ton of algae, this couldn’t work. I personally have a fully stocked tank FILLED with valisneria, and I only have to do wc once a month. Besides top offs. But I’m sure it could be prolonged if I had a smaller stock and edited other components too.

I agree, plants significantly help with nitrate removal, I can't argue with Walstad, I will just say that:
1. it's not a guidebook, or a religion, like dianetics, it's simply a means for people to better understand how a low tech planted tank works.
2. that's not how a lot of folks want to be in the aquarium hobby, keeping water and plants as majority and a couple small fish. Most folks, until they mature in the hobby and look for a tougher challenge, want to keep the fish and see everything else as "accessories or decorations", and are looking for that 10x filtration or better to keep a ton of fish, it's the reason the "fishless cycling" directions pushes 2ppm ammonia, so you can stock out an aquarium immediately with fish, because that's what most people want.
3. Kinda is a salesman, just saying she's selling books now a days, she was a scientist, now she's an author.

I agree, you probably could do 2 water changes a year, maybe just one or none if you stopped keeping fish entirely and just kept water and plants, and made some tweeks.
I'm not knocking it, some people really like scaping and plants. It's not why most people get into aquarium keeping though (note I didn't use fishkeeping exclusively, lots of ways to keep aquariums for many different things, just saying the majority are in the hobby to keep fish or animals in general, there's easier ways to garden than doing it submerged in water). They are here cycling for 2ppm, and here buying filters for 10x filtration. it's when we get bored with fish, we go down the rabbitholes to the "no water changes" or " full nitrogen cycle", or the Walstad "method". aquascape styles, "nature", "iwagumi" , or go down the no filter path, or the full blown high tech and CO2 path.

 

But this is kind of what I mean, the farm pond has evaporation to contend with, if there isn't rainfall, then the water continues to condense, maybe farm use drops the level further and further also to water plants or cows. maybe it drops to a certain point and ground water seeps upward maintaining the level also at a baseline. Maybe if you put up the 4 walls of that 40K gallon tank, in a decade or two, you get enough buildup and mud on the bottom to get a similar substrate to the bottom of the pond, that has aerobic and anaerobic bacteria, that the water then runs all cycles and can support life, but that pond or tank is still a cold snap or a heat wave or a drought away from a bloom and bust and rebirth or,,, a dead pond.

Unless it's spring fed I don't believe you're going to get any ground water into an existing pond. If the bottom was that porous it wouldn't hold water.

 

The source is irrelevant. Top-offs with too mineral rich water only make said minerals build up and up and up. That's how many people even with moderately soft water end up with incredibly high GH and KH levels when only topping off. There are dozens of cases here on the forum that went exactly like that.
The problem is evaporation removes only water. everything in it is left behind.

from my experience, the KH doesn't wind up high, it can't. old water eventually runs out of buffer unless there's a significant method of replenishment, carbons start stacking and KH gets run down as GH skyrockets.
Even now my KH and GH are screwed up, and my pH is still low (it tests at 6 might be lower) even though I've cleared out the bulk of the nitrates and trying to keep it between 20 and 100 ppm during a week period.(my stocking, I gain a lot of nitrates every day)
My GH is still like 17dGH, a lot better than 20-25dGH. my KH is still reading zero on tests if its there it's minimal and just traces of carbonates, I don't know if it can go any lower or not really. nitrates are lower than they ever have been though. Fish can acclimate smoothly. I don't know, it's works and nobody is dying I can move a fish from 6.8 pH or 7.2 pH with 6GH and 6KH directly to the 6 or less pH and 17 GH and 0KH, with out any issue, and I can move fish from there to the other tanks as well immediately without needing to acclimate.

Whatever I accomplished from all the water changing that basically just removed nitrates and didn't fix other parameters too much, it totally stopped the osmotic shock, I wish I knew more about the science of it all.

 

from my experience, the KH doesn't wind up high, it can't. old water eventually runs out of buffer unless there's a significant method of replenishment, carbons start stacking and KH gets run down as GH skyrockets.

Depends on the actual numbers, evaporation rate and how much carbonate is used up by the tank's biome. Long term, surely, carbonates go down. If evaporation and top-off happen faster than the consumption, carbonates still rise. Once consumption exceeds influx it turns.

 

Unless it's spring fed I don't believe you're going to get any ground water into an existing pond. If the bottom was that porous it wouldn't hold water.

it's a bit more complex than that, hydrostatic pressure, gravity, water weight above and pressure below, elevation and the water table, and perhaps aquifers below... there's a lot of variables besides a river or a spring feeding it.

I feel like reiterating my position on the whole "no water change" tank thing. I think it's plausible,just not with a singular method of nitrate removal, but by using all methods available to reduce nitrates and testing to monitor excesses and depletion of nutrients as well as gasses, in order to find a balance that gets you that no water change result while not having to keep a tank full of plants, while being able to keep more than a few small fish. I know I have a reduction in my filter now, and I think I'm going to try marine pure block next there on top of matrix and see if there is a gain beyond what the matrix is doing. I think If I do something with my substrate, anoxic zone through substrate layering or plenum nonsense from youtube, I can have a second anoxic location besides the pores of media for even more denitrifyers. If plants were then added to take out even more through usage, I think it could get it over that hump to run a zero and not be massively planted and have decent stocking to boot.
HOWEVER, This still doesn't address all the other buildups or depletions that can occur that need to be addressed, it just addresses the nitrates. not nutrients or minerals, or gasses.

I still think I can have a low to no nitrite tank if I used a 2nd 72 gallon tank that was heavily planted as a sump so one tank is just plants for filtering through, and the other tank is just fish. Sure takes up a lot of space, but I think it could work with all plants in one, all fish in the other and the water passing between them.

Come to think of it, why couldn't I bury a marinepure block or two under a couple inches of substrate and let those blocks be little hills of anoxic zones in the tank? do they have to be slabbed in a filter? Couldn't you just stack up a half dozen and bury it under dirt and sand and make a mountain with a top secret nitrate grinding base underneath it? I guess it gets jammed up or something.....