In search of middle-earth - a quest for a middle energy tank

[Yugang]

I'm not sure about 10ppm, though I'm quite sure 15ppm will do it based on what I observe in tanks where I have taken accurate readings

more light to get enough branching to get a very dense canopy (you will probably need at least 200umols at the canopy area

Thank you @Dennis Wong , sharing your experience is extremely valuable for this thread and for my tank. I took a hint from @sudiorca tank, but I now see you and a few others in this thread confirm that low CO2 and medium high light can be a good combination.

I guess the (medium) high light may limit the compromises as compared to a proper high tech tank with 30+ ppm or so, and we don't need to settle either with the limitations of a low tech tank with regard to lush growth and coloration.

If the tank in your post is a realistic goal then I don't see much of a compromise in that.

I will continue on this track, and my drop checker will remain at 2 dKH to keep the tank on the 15 ppm target. I only need a really small CO2 Spray Bar to stabilise it. It would be great if we could continue to share experiences, as I am probably not the only one who feels this approach deserves a bit more attention. Not sure why currently probably >95% of the drop checkers are set at 4 dKH and we generally advise a 1 pH drop for dialling in CO2?

 

[Krandall]

The method I’ve always followed requires repeated cycles of “soaking” and allowing to dry via sunlight. This results in a sandy/airy substrate and this stage I was under the impression was the “mineralized” state. I have not had issues with this practice

Yes, that is exactly the process that Sean originally designed.

 

[Krandall]

But managing the CO2 angle is definitely the key in having a successful low tech tank. Folks have it wrong then the approach low tech tanks thinking that they can work without CO2 - it is the opposite, the key is setting up a low tech system that generates meaningful CO2.

Absolutely! I have been saying this for years. You cannot have a successful tank, even with the slowest growth plants, without CO2. It is just a matter of where the CO2 is coming from. All plants MUST have access to CO2 for growth. From somewhere. It is a matter of figuring out how you want to provide it.

It is fantastic, Dennis, that you have the equipment, and have taken the time to actually go around and measure tis in various styles of tanks!

I think that about sums it up right there. A great and smart way to think about it. I’m wondering then if it would be ideal to run a filter in the hours in which the lights are not on so as to not have that off gassing that would impact a non injected tank. Is that too simple of a solution?

I am not positive, but I doubt it. In the non-injected tank, one of the things you are counting on is the build-up of CO2 during the overnight hours. I think what helped in the “old days” is that people with larger tanks, (who were the ones who also tended to do better with plants) used canister filters with the return well below the surface, to avoid as much surface agitation as possible. The other big difference is that they tended to have a LOT of larger fish. Not huge fish, necessarily, but bigger than the tiny schoolers we typically think of for planted tanks now. Rainbows, angels, Congo tetras… “bread and butter” aquarium fish, and large numbers. That large number of fish, and the food they were fed added to the CO2 in the water.

But the problm was that it was really hard to replicate this for someone else. Particularly because they knew nothing about the water chemistry, or WHY what they did worked.

(I can try to find some photos of tanks like this later, but I’d have to go back into slides, so it won’t be quick!!! this would be pre-digital!)

If you look at emersed plants produced by companies cattering the hobby I wouldn't be surpised they did the same thing by increasing the CO2 concentration in their greenhouses. Maybe, maybe not but, in commercial greenhouses producing vegetables, I am certain they do it to increase yield.

I can speak to this directly , since I have visited many of the major plant producers in person over the years. They do not. I can’t tell you that none do, but none of the “big guys” do.

Among the many picky species in high tech tanks, the ones that do respond quickly to increased CO2 levels (say from 20 to 35ppm) that I can spot are the red Erio, Blood vomit, and S. Vichada, to less extent, Hygrophila sp Chai. For many other common species such as Rotala rotundifolia variants/macrandras, most ludwigias, I cannot spot the difference between a 20ppm vs 35ppm tank even with all my expertise.

This goes along exactly with what I would expect considering the conditions where these plants are found in the wild.

 

[RickyV]

I think what helped in the “old days” is that people with larger tanks, (who were the ones who also tended to do better with plants) used canister filters with the return well below the surface, to avoid as much surface agitation as possible.

I am glad this topic was brought up because I have been wondering what the best placement of my return is for my low tech tank. In the CO2 injected tank I aimed to have plenty of gas exchange for both CO2 stability and giving the fish plenty of oxygen to deal with the higher CO2 levels. But in a low tech tank it sounds like we want to take the opposite approach? But won't this reduce oxygen levels too much? Or are the plants really generating that much oxygen even in a low tech tank?

 

[ElleDee]

IMO, may people who try to work with soil use “potting soil” or commercial “top soil”. Both are largely organic material, and likely to cause big problems In the bottom of an aquarium, especially if used in large amounts. Then people DO use them in large amounts. Not just a handful or two mixed into the bottom layer of gravel.

I fully understand the concern here, though I went down this road with my first few tanks and never had a problem. I suspect this is because the mix I used is mostly pine bark and sphagnum moss and fairly recalcitrant to decomposition as far as organic material goes and I didn't make the layer too deep, but that's just my best guess. My oldest tank is coming up on 4.5 years and still going strong, though in that duration I've watched other people crash and burn who too a similar approach. I suspect there's some conceptual knowledge missing in the hobby here, but organic matter in the substrate is a complicated topic.

I hope you are joking, and know that mineralizing top soil requires actually submerging it in water for an extended period of time, right?

I'm only kind of joking. My understanding of the procedure is that it is a very quick way to decompose the organic matter and leech out most of the nutrients, but it's not the only way to achieve those goals. The bag composting on the sidewalk is going through the same process, just much more slowly. Doing a dark start should also achieve pretty much the same thing. At any rate, the submersion step is not when the majority of the actual mineralization happens, as organic matter breaks down way faster in moist soil exposed to air than when inundated. Don't get me wrong, Sean Murphy's method has been very successful for people, but, again - I'm just too lazy.

@Dennis Wong, I would read the hell out of a deep dive on CO2 generation in non-injected tanks if you ever find the time! We could really use some new, data-driven thinking on the topic, as I find are some gaps in the old standard advice/theory. You have a great skill for taking seemingly conflicting schools of thought and coming up with a framework that accounts for both and we could use that here! There's a lot of friction between the idea that organic decomposition is the primary driver of CO2, yet also greatly feared as a source of algae and other troubles. Your data about co2 in fish-only tanks are also interesting; that's a similar example where the potential for CO2 generation goes hand in hand with algae, and the prevailing advice has always been to keep a light bioload and minimize water changes. Concerns about gas exchange is another area where there is a lot of conflicting information, due to emphasis in some corners on the importance of dissolved oxygen coming up against concerns about off gassing. Those are issues that I have repeatedly come across, including in this thread, but really anything new you add to this topic would be appreciated.

 

[Krandall]

the prevailing advice has always been to keep a light bioload and minimize water changes.

This is "Internet advice". Those of us who get out there and see lots of tanks kept by lots of aquarist over lots of years know that it doesn't necessarily hold up. If you could have seen the bio load in George Booth's tanks.

Minimizing water changes is new to me! when did this start? Probably with the regular use of RO/DI water?

 

[sudiorca]

But in a low tech tank it sounds like we want to take the opposite approach?

This is not entirely true. I have been able to measure daily pH difference of about 0.3-0.6 units (low pH in dark period due to respiration and high pH during light period due to photosynthesis) in most of my non-CO2 supplemented softwater tanks with decent surface agitation and water circulation. CO2 is about 26 times more soluble in water than O2. Its ability to react with water to form carbonic acid along with forming hydrogen bond with water makes it significantly more soluble in water than O2. This is the primary reason why most people struggle to fully degas their pressurized CO2 injected high-tech tanks.
It is important to understand the difference between exogenous CO2 coming from atmospheric dissolution and CO2 generated inside the tank by respiration. I mentioned this in my AGA talk earlier this year how atmospheric dissolution will only add about 0.5-0.6 ppm CO2 in tank water due to 10000 fold slower diffusion of gases in water compared to air and the fact that the partial pressure of CO2 is very low in the atmosphere (CO2 concentration is only 0.04% in the atmosphere compared to 21% of O2).
CO2 generated inside the tank due to respiration (from plants, livestock and microbes) will react with water and form hydrogen bonds with water leading to higher CO2 concentration in water. It doesn't easily escape from the water even with decent surface agitation and water circulation. Low pH and relatively lower temperature also help in this regard. This is an old video of my 20 gal non-CO2 supplemented softwater tank which I successfully maintained for almost 4 years. I used an oversized hob filter (Aquaclear 70) in this tank which allowed good water circulation throughout the tank along with decent surface agitation (skip to 1:25 if you just want to see surface agitation).

But won't this reduce oxygen levels too much?

Yes, it does significantly reduce O2 concentration in night (3-4 hours after the lights turn off). Here is my filterless 1.5 gal jar and you can see all the shrimps aggregated at the top of the driftwood close to the surface suggesting lack of O2 in water. They do this everyday, stay on top until the lights turn on. However, they have been breeding quite frequently and the population has increased significantly since I added them here.

 

[Krandall]

I am glad this topic was brought up because I have been wondering what the best placement of my return is for my low tech tank. In the CO2 injected tank I aimed to have plenty of gas exchange for both CO2 stability and giving the fish plenty of oxygen to deal with the higher CO2 levels. But in a low tech tank it sounds like we want to take the opposite approach? But won't this reduce oxygen levels too much? Or are the plants really generating that much oxygen even in a low tech tank?

I am sure "it depends". On the plant mass, the health of the plants, the fish mass, the feeding, the cleanliness, etc. I can tell you that it has not been a problem for me.

 

[ElleDee]

This is "Internet advice". Those of us who get out there and see lots of tanks kept by lots of aquarist over lots of years know that it doesn't necessarily hold up. If you could have seen the bio load in George Booth's tanks.

I haven't pushed bioload myself yet for unrelated reasons, but that's good to hear. I like fish so much and intend to get full stocked eventually, but I am still fairly inexperienced with them and separating good advice from the bad is not always obvious.

Minimizing water changes is new to me! when did this start? Probably with the regular use of RO/DI water?

Sorry, I need to clarify. There has long been an association between minimal water changes and low tech tanks, especially those closely following Walstad or into more "ecosystem" type setups. A big appeal of low tech tanks is that they are lower maintenance, so there are lot of people who take full advantage of that fact and I definitely feel like an outlier doing a 50% weekly WC without CO2-injection. I *could* get away with less and do if I get busy, but things run better if I stay on it.

But with regards to actually minimizing water changes, there is an old write up from Tom Barr where says large water changes will confuse the plants about whether they need to be adapted to a high- or low-CO2 environment and allow algae to get the upper hand. I am not one of those folks with some kind of weird one sided beef with Tom, but I am skeptical this is a real problem in practice. Even though this post is from 2005(!), I have seen it referenced multiple times in the last year by different people, so it's still informing the current thinking.

 

[Krandall]

You know, I would always go back to the source and ask him directly what his thoughts were on a 19 year old article. He's always around. I'm not going to speak for him.

 

[Mr.Shenanagins]

@plantbrain He’s on here, maybe he’ll chime in

 

[plantbrain]

Okay, what’d I do now???

Water changes can help non CO2 tanks the same reasons why they help co2 enriched tanks.

Confused I suppose if you look at rubisco context and stability. Non CO2 enriched tanks plants have higher rubisco content. They need it. Enriched CO2 tank plants have less, they don’t need a lot. In that context, water changes might help non CO2 tanks. I’ve done both but the bottom line and reason for non CO2 is slower , much slower growth. Less labor and few if any water changes. So adding water changes beyond the start up is less the goal for non CO2. I prefer just using the gas and picking more suitable plants that grow slow. Wise decision rather than avoiding the gas “just because”. If you are doing it to test the benefits/trade offs for yourself, sure. But the specific goal is always the start point. A low light, CO2 enriched tank, well hardscaped….well chosen plants are often many of the top scape rankings in most of the international contest. Something to ponder.

A few folks have expanded the species that normally have been kept. I’ve grown them as well that way.

A third option is no water change CO2 rich(. 40-70 ppm) and no ferts really other than the soil. I feed the shrimps etc. keep a few fish. This plus the bioload, ADA aqua soil combines a few methods. Pps/pmdd , without the dosing. Why bother ? Not needed. Then part of the MTS/soil approach which also seems to suggest traces etc are needed, turns out they are not…with ada AquaSoil.

I’ve done this for nearly a decade. I can scape, grow pretty much any rare or the most difficult stem or rossette plant. Light is about 100 umols at the sediment.

Low light CO2 contest tanks are about 40-50 umols. Most of the older ADA tanks from Amano’s books are all in that range. Light is the gas pedal.

 

[plantbrain]

Okay, what’d I do now???

Water changes can help non CO2 tanks the same reasons why they help co2 enriched tanks.

Confused I suppose if you look at rubisco context and stability. Non CO2 enriched tanks plants have higher rubisco content. They need it. Enriched CO2 tank plants have less, they don’t need a lot. In that context, water changes might help non CO2 tanks. I’ve done both but the bottom line and reason for non CO2 is slower , much slower growth. Less labor and few if any water changes. So adding water changes beyond the start up is less the goal for non CO2. I prefer just using the gas and picking more suitable plants that grow slow. Wise decision rather than avoiding the gas “just because”. If you are doing it to test the benefits/trade offs for yourself, sure. But the specific goal is always the start point. A low light, CO2 enriched tank, well hardscaped….well chosen plants are often many of the top scape rankings in most of the international contest. Something to ponder.

A few folks have expanded the species that normally have been kept. I’ve grown them as well that way.

A third option is no water change CO2 rich(. 40-70 ppm) and no ferts really other than the soil. I feed the shrimps etc. keep a few fish. This plus the bioload, ADA aqua soil combines a few methods. Pps/pmdd , without the dosing. Why bother ? Not needed. Then part of the MTS/soil approach which also seems to suggest traces etc are needed, turns out they are not…with ada AquaSoil.

I’ve done this for nearly a decade. I can scape, grow pretty much any rare or the most difficult stem or rossette plant. Light is about 100 umols at the sediment.

Low light CO2 contest tanks are about 40-50 umols. Most of the older ADA tanks from Amano’s books are all in that range. Light is the gas pedal.

This said, if you gas a tank good, then turn off the gas for awhile, generally you will get a hair algae bloom in many stem plant tanks. You can prevent and mitigate this with water changes, lots and large ones for a couple of weeks then things settle in nicely. Many suggest gas the tank at the start to fill in, then yank the GAS. Not a bad idea either, similar to dry start method. Another pox I suggested at one point.

 

[Yugang]

From the discussion above I believe that we can take that it is possible to have a nice tank at 15 ppm CO2. Two weeks into my experiment, I see my tank recovering, so frankly a little bit impatience kicks in...

I believe it Is worth trying even lower CO2 and see what that does. I made a smaller version of CO2 Spray Bar, use it in overflow mode so that I have a really stable 24/7 injection rate. My 2 dKH drop checker is not quite lime green, so my best guess is that I am now slightly above 10 ppm CO2, but definitely below 15 ppm.

lower maintenance and MUCH lower CO2 consumption

Counting the CO2 bubbles injected in the CO2 Spray Bar, and estimating bubble size from a slow-mo video, I now expect my 2 litre CO2 bottle to last more than a year on one fill, and this is with 24/7 injection. My assumption is that this continuous injection will help stabilise CO2 as there is no ramp up/down and benefit the plants, but perhaps also be more comfortable for livestock? As I use overflow mode, the CO2 Spray Bar stabilises CO2, so ideally for the next year I can ignore my CO2 and trust simplicity to work for me.



I will settle on this injection rate and see how the tank does over the next couple of weeks. Some plants will react fast, but others in my experience need much more time to show how they will react.

 

[Krandall]

To illustrate Tom’s point about just a small amount of added CO2 doing an amazing amount of good in an otherwise “low tech” tank, here are two sets of photos. This first is WAY back when I was beta resting the Seachem product line for them. They did not want me to run CO2 on the tank, because they wanted me to use Excel (a then, brand new idea) Not terible for a Flourite/no CO2 tank, especially remembering that at this pint they had not added NPK to their product line. So that ONLY came from feeding a a good sized school of adult Dennisoni barbs in the tank. (The first ones in the country… lovingly hand carried in my hand luggage from the Wet Spot! Can’t do that any more!)



This second photo was after I had finished the testing, and threw a very small yeast reactor made by Fluval on there (anyone remember the little bubble ladder?) just to try it out. This was about 6 weeks later. I was no stranger to supplemental CO2 at that point, but I was astonished that so little could make such a big difference.


This second set was done more recently, and more intentionally, because I wanted better quality photos of the same thing. So I did this shortly before writing my book. The plant choices and scaping were a bit more intentional, but the results are the same. A SMALL amount of supplemental CO2 making a huge improvement in growth in an otherwise “low tech” tank.

Here, it had been set up and running for about 4 months, A pleasant, easy, slow growth tank. You can see I had just put a CO2 reaction chamber in on the left to start adding CO2.


This final photo was 2 months later. I can’t give you exact amounts of CO2 I was adding, but it wasn’t being added efficiently, and I didn’t really care. So I’m sure it was not high. The plants still responded! However, from a maintenance standpoint, the Limnophila was now a royal pain in the neck!

 

[GreggZ]

But managing the CO2 angle is definitely the key in having a successful low tech tank. Folks have it wrong then the approach low tech tanks thinking that they can work without CO2 - it is the opposite, the key is setting up a low tech system that generates meaningful CO2.

Hey Dennis first of all great to see you posting here. With you, @plantbrain, and @Krandall all in the same thread that is a LOT of planted tank brain power!!

To your point above. A year or two ago I had a malfunction with the filter that drives my Cerges reactor and had to wait about a week to get parts. So I let the tank go without CO2 for the entire time. Mostly just to see what would happen.

I tracked the pH very closely as I was curious what it would do. My tank runs at very close to zero dKH with pure RO. Fully degassed reading right from the RO storage is 6.4. Fully degassed from the tank is 6.25. But here’s where it gets interesting.

First thing in the morning the pH in the tank was consistently about 5.85. That’s a 0.4 pH drop overnight. So the pH slowly rose during the day while plants were consuming, then dropped slowly overnight. Happened the same way everyday.

Now I don't know how much CO2 was actually being generated without a meter like yours, but clearly the tank was generating a decent amount of CO2. Way more than I expected.

 

[Krandall]

Of course, that is EXACTLY what happens in the wild in small bodies of water.

 

[hypnogogia]

First thing in the morning the pH in the tank was consistently about 5.85. That’s a 0.4 pH drop overnight. So the pH slowly rose during the day while plants were consuming, then dropped slowly overnight. Happened the same way everyday.

And that measurement can be used to supplement the tank with co2. By setting the co2 monitor at just above the morning level, it will come on as the oh rises, but stay off overnight as the ph drops again. In this way you provide the plant with the amount of co2 that they consume.

 

[Krandall]

I don’t think this is a given. I think in many (perhaps not all) low Light/slow growth/non-CO2 supplemented tanks, CO2 is the limiting growth factor. I am sure that plants use up all that is readily available well before their growth potential is reached in these systems. We certainly see that often in small wild bodies of water, where pH is SKY high in the afternoon, and biogenic decalcification is common. This used to be pretty commonly seen in some aquariums too.

 

[Dennis Wong]

Hey Dennis first of all great to see you posting here. With you, @plantbrain, and @Krandall all in the same thread that is a LOT of planted tank brain power!!

To your point above. A year or two ago I had a malfunction with the filter that drives my Cerges reactor and had to wait about a week to get parts. So I let the tank go without CO2 for the entire time. Mostly just to see what would happen.

I tracked the pH very closely as I was curious what it would do. My tank runs at very close to zero dKH with pure RO. Fully degassed reading right from the RO storage is 6.4. Fully degassed from the tank is 6.25. But here’s where it gets interesting.

First thing in the morning the pH in the tank was consistently about 5.85. That’s a 0.4 pH drop overnight. So the pH slowly rose during the day while plants were consuming, then dropped slowly overnight. Happened the same way everyday.

Now I don't know how much CO2 was actually being generated without a meter like yours, but clearly the tank was generating a decent amount of CO2. Way more than I expected.

Hey man, sorry for not posting much here, it has been a busy year. I think matured filters/substrates (even without soils) produce some CO2, for fish-only tanks at shops, I could measure 5-6ppm of CO2, whether its from the fish itself (less likely?) or the microbial action of matured filters. I think data need to be gathered so that finally we can give better advice to low tech folks. I need an intern to make better use of the equipment, its sitting around most of the time.