Interaction of aquatic plants with bacteria - should we care?

[Art]

I ran into a very interesting study that discusses plant-microbe interaction in aquatic systems. It has this very interesting graphic that describes the interaction of plants and bacteria along with the outcomes.



This got me thinking of how this would work in our aquarium environments and whether we should care. I know ADA has always focused on the microorganisms in the substrate and considered them quite important to the overall ecosystem. Their PowerSand and AquaSoil substrate system, along with the additives, speak to that.

However, many, many of us have had very good success with inert substrates where plants are pulled up and cuttings replanted often. Certainly the substrate is disturbed along with the microorganisms living in it. So should we even consider it? Should we care?

There are studies that show that bacteria and algae do have an antagonistic relationship with bacteria releasing allelochemicals that impact algae and not plants. Perhaps there is more to think about here??

 

[Joel Armstrong]

This is a topic I am very interested in. And yes, I would say we should care, and that there is more to think about.

Sadly, I can not really offer anything meaningful to this thread, but I'm very interested to learn more about it.

 

[ElleDee]

Yeah, I think microbes are incredibly important above and beyond the small subset involved in nitrogen cycling that tend to get all the focus. They provide most of the CO2 in my tanks, and from a philosophical standpoint I like the idea of having a healthy, diverse microbiome to help keep things balanced. How to achieve that though?

I wish I had more details about the ADA additives because I like the concept, but at that price point I'm not going willing to just buy them and see what happens. Oftentimes a solid theoretical basis does not result in a practical difference. I've heard that it's overrated and that powersand has no read advantage over lava rock, but I can't verify that one way or another. I imagine that with time the microbes sort themselves out without any additives, so any advantage would be restricted to the startup period.

 

[Art]

So here is a very old post I did when I was doing ScapeFu: The aquarium to test the Radion. It covers some of the ADA substrate additives. I also imported Power Sand into the US back in the day and so was told exactly what was in it for import duties and reporting. I did a DIY version a few times.

I think the point Amano had was that we are all building an ecosystem following the example of Mother Nature. There is no need to change it , just learn from her and follow it. So, he understood that the substrate is a different environment than the water column and it will have its own important ecosystem that we must respect and cultivate, even though we may not completely understand it.

Power Sand, IMO and back in the day, was mostly composed of pumice stone and peat. This created space in the substrate to allow for bacterial and microorganism growth and avoid compaction. The idea was to make the substrate low oxygen but not no oxygen.

The peat brought the pH of the substrate solution down to a level that kept certain nutrients in solution and bioavailable. Again, the thinking was to provide as ideal as possible the conditions for nutrient cycling in the substrate.

It was recommended to add crushed carbon as a layer over the PowerSand as this would remove much of the coloring released by the peat and also provide a home for needed microbes. ADA would provide bacterial powder to add over this to seed the substrate with bacteria (query whether they knew what bacteria and if it was the right kind). All of this combined into one is Power Sand Special.

Of course, this is just my observation and what I was told. Perhaps today it has something else.

What I can say is that when I used the ADA substrate system in my past tanks AND those tanks were set up for long term setups (i.e., no constant stem replacement), they were some of the best tanks I've maintained. Algae was always very manageable and conditions where usually very healthy.

 

[Art]

I imagine that with time the microbes sort themselves out without any additives, so any advantage would be restricted to the startup period.

I think this is very true. At some point, all well maintained aquariums will reach a maturity point where the substrate has the needed microenvironment to flourish. However, if it is disturbed by constant uprooting or re-scaping, perhaps it never reaches the optimal state.

And, maybe in high-energy tanks, the substrate matters less in terms of plant growth. However, I think in middle and low-energy tanks, the substrate plays a much more crucial role.

Does anyone know what processes happen in the substrate that cycle nutrients?

 

[ElleDee]

I think this is very true. At some point, all well maintained aquariums will reach a maturity point where the substrate has the needed microenvironment to flourish. However, if it is disturbed by constant uprooting or re-scaping, perhaps it never reaches the optimal state.

And, maybe in high-energy tanks, the substrate matters less in terms of plant growth. However, I think in middle and low-energy tanks, the substrate plays a much more crucial role.

Yeah, I suspect that's true. It's similar the differences between "build the soil" type gardening compared to conventional farming systems that rely on heaving tilling and fertilizer application. One is focused on maximum yield, high turn over, with input variables that can be tightly controlled, the other tries to indirectly support a concert of natural processes that contribute to plant growth. Different approaches with different goals.

Does anyone know what processes happen in the substrate that cycle nutrients?

Nitrification, decomposition, and soil weathering are all microbe-facilitated processes that generated plant-available nutrients. I don't know that much weathering happens in our tanks, but it's important in natural soils. There are probably others that I'm not thinking of right now. When those nutrients are incorporated into organic matter (plant or microbe biomass) they are immobilized again, and when that biomass decomposes will become mineralized and the cycle continues. *cue Circle of Life* Obviously these processes are not just restricted to the substrate, but the substrate has (potentially) massive surface area, is largely undisturbed (more so in high energy tanks, as you've noted), and can support lots of microbial diversity in its many different environmental niches due to things like redox, the presence of plant roots, etc.

Now that I've typed it all out, it may just be that it matters more in lower energy systems because endogenous CO2 generation is way more important and so anything that increases microbial respiration is going to be better, period. That is a much less satisfying answer to me conceptually, but that doesn't mean it's wrong.

 

[Art]

I think @ElleDee that the substrate does a lot more than we think in all tank versions.

it may just be that it matters more in lower energy systems because endogenous CO2 generation is way more important and so anything that increases microbial respiration is going to be better, period.

So back in the day, I experimented with dosing vodka into a non-CO2 supplemented tank. I used slow growing plants (anubias and some crypts) thinking that I needed low-energy plants. My hypothesis was that increasing the bacterial population would increase microbial respiration thereby increasing CO2 in the system.

I never really finished the experiment to my satisfaction because I got a cyanobacteria outbreak of epic proportions. Probably increased dosing too fast.

Something to think about.

Also, the cation exchange capacity of substrate will cause it to function as a nutrient storehouse for plants. It can take excess nutrients from the water column and bind them until a plant root causes it to release it. Wouldn't this theoretically help in keeping algae at bay given that algae can't access these stored nutrients?

 

[ElleDee]

@Art this inspired me to crack open my old soil science textbook. I've taken pictures of all the nutrient cycling diagrams and have posted them below for anyone who might be interested. It gives a much fuller picture of the fate of nutrients in the tank. (I apologize if this is overkill.)

There's a lot going on in each diagram, but even though each nutrient cycle is a little different, there is a lot of commonality and elements relevant to our tanks that I have highlighted, though the terminology isn't exactly the same in every diagram:

Blue - Nutrients in the soil solution, ready for uptake. These are the only nutrients that are directly available to plants. All must go through this step to be used by a plant.
Green - Nutrients contained in biomass, or mediated by soil organisms
Yellow - Nutrients adsorbed onto a surface (this is where CEC comes in)
Purple - exogenous fertilizer
Red - sources of organic material (in our tanks that includes fish waste, aquasoil, organic potting mix, botanicals, and plant root lysates/exudates/mucilages)

(I did this very quickly, hopefully I didn't make any mistakes but no promises.) You can see the connection between organic matter > microbes > available nutrients, and you can see that just adding fertilizer bypasses that process. Charged particles/surfaces adsorb and desorb ions regardless of their origin and can hold them in the substrate. It may be worth noting that while we don't have leaching and erosion per se, that's essentially what is happening when we remove nutrients through water changes.

Nitrogen:

Potassium:

Phosphorus:

Sulphur (I don't think we learned this one at all, or I blocked it out. I will not be taking any sulphur cycle questions lol):

Calcium and magnesium:

Micronutrients:


These are from chapter 12 of Elements of Nature and Properties of Soils, Third Edition by Brady and Weil.

 

[Yugang]

I am a firm believer that the microbes living in the soil are an essential part of the tanks maturity. There are plenty of examples where messing with the soil in an otherwise healthy and mature tank triggers problems.

Unlike terrestrial plants, aquatic plants have the capability to benefit from their large leaf surface area in the water column to absorb nutrients.

Now if we make the assumption that the soil supports the plants, is it fair to say that this could only happen through well developed plant root systems, or alternatively the soil leaking CO2 and nutrients into the water column so that the plant uses its leaves to benefit from these?

The processes in the soil are essential for elevated CO2 (as compared to ambient air) in non-injected tanks - check.
When we choose to add only very limited fertilisers to the water column, then the survival of plants depends on the soil - check.

How many plants do we know that ONLY thrive with a well developed root system? How many of our plants in high energy tanks are replanted before they have even developed a good root system, and are perfectly fine with that?

I have seen several of examples, @GreggZ and others, that inert substrates perform no less than aqua soils, not even to mention all the additives that are for sale. Show me one example where soil supplements were essential in a well dosed tank, I have not seen it yet.

My personal opinion is that the only thing that can be objectively proven is the marketing drive behind soil and soil additives and the cash out for the hobbyist. It's like our own food supplements, for a healthy individual with a healthy diet most of them are not needed whatsoever. But food supplements is a really big market, and many doctors and retailers are in the pocket of this industry. I am using 5 years old AquaSoil, but with next rescape I will invest in an inert substrate that I can use and reuse indefinitely.

 

[ElleDee]

How many plants do we know that ONLY thrive with a well developed root system? How many of our plants in high energy tanks are replanted before they have even developed a good root system, and are perfectly fine with that?

Do crypts, swords, hair grass, or bulb plants thrive in high energy tanks without root systems? Honest question, because I've not experience with that kind of tank.

I have seen several of examples, @GreggZ and others, that inert substrates perform no less than aqua soils, not even to mention all the additives that are for sale. Show me one example where soil supplements were essential in a well dosed tank, I have not seen it yet.

My personal opinion is that the only thing that can be objectively proven is the marketing drive behind soil and soil additives and the cash out for the hobbyist. It's like our own food supplements, for a healthy individual with a healthy diet most of them are not needed whatsoever. But food supplements is a really big market, and many doctors and retailers are in the pocket of this industry. I am using 5 years old AquaSoil, but with next rescape I will invest in an inert substrate that I can use and reuse indefinitely.

I don't disagree with you. I think it's more a matter of plants having needs that have to be met, and the substrate can serve some of those needs or you can do it all yourself. If your techniques are on point then no problem, but otherwise the soil processes can potentially buffer against inconsistencies and minor missteps. If you don't need the buffer, then inert substrates are definitely cheaper and last forever, so I see the appeal for CO2 injected tanks. (I do not understand low tech tanks with inert substates. Sounds like a tough row to hoe if you want to grow more than the least demanding plants.)

 

[Yugang]

Do crypts, swords, hair grass, or bulb plants thrive in high energy tanks without root systems? Honest question, because I've not experience with that kind of tank.

True, and some believe that root tabs are helpful for these plants. But first these are a minority of the species we use, secondly I have never seen any evidence that they can't be grown successfully with good water dosing. I have seen evidence however that top tanks with inert substrates work, @Gregg is one of them and there are many others. I believe the point is that good substrates and additives do no harm (except for our wallet and that once in the tank they cannot be easily removed), and can definitely help, but that there are easier and more economical ways to get good results.

Oftentimes a solid theoretical basis does not result in a practical difference.

Fully agree @ElleDee. It is satisfying to have a mental model of our environment, even if not based on evidence and observations. We are then more than happy for marketeers to feed us "scientific arguments" to reduce perceived uncertainty and justify our ideas and decisions. Even more so when a community shares same mental models which makes us feel even more confident. Sometimes scientific papers are valuable in themselves but mostly without direct and scientifically robust relevance to our hobby. Marketeers understand this, and this is how some brands built their business without actually presenting any evidence of efficacy for our hobby. I find this fascinating to observe, but also I enjoy trying to peel back the onion and see where is the real stuff to make a successful tank.

 

[Dennis Wong]

I am a firm believer that the microbes living in the soil are an essential part of the tanks maturity. There are plenty of examples where messing with the soil in an otherwise healthy and mature tank triggers problems.

Unlike terrestrial plants, aquatic plants have the capability to benefit from their large leaf surface area in the water column to absorb nutrients.

Now if we make the assumption that the soil supports the plants, is it fair to say that this could only happen through well developed plant root systems, or alternatively the soil leaking CO2 and nutrients into the water column so that the plant uses its leaves to benefit from these?

The processes in the soil are essential for elevated CO2 (as compared to ambient air) in non-injected tanks - check.
When we choose to add only very limited fertilisers to the water column, then the survival of plants depends on the soil - check.

How many plants do we know that ONLY thrive with a well developed root system? How many of our plants in high energy tanks are replanted before they have even developed a good root system, and are perfectly fine with that?

I have seen several of examples, @GreggZ and others, that inert substrates perform no less than aqua soils, not even to mention all the additives that are for sale. Show me one example where soil supplements were essential in a well dosed tank, I have not seen it yet.

My personal opinion is that the only thing that can be objectively proven is the marketing drive behind soil and soil additives and the cash out for the hobbyist. It's like our own food supplements, for a healthy individual with a healthy diet most of them are not needed whatsoever. But food supplements is a really big market, and many doctors and retailers are in the pocket of this industry. I am using 5 years old AquaSoil, but with next rescape I will invest in an inert substrate that I can use and reuse indefinitely.

You can see some examples of root feeding impact vs inert substrates in my link: Root or water column fertilization?
There are plenty of differences, you just can't tell until you examine close-ups of plant growth forms. Many folks post only full tank shots, while their close-ups don't stand up to scrutiny~

 

[Yugang]

You can see some examples of root feeding impact vs inert substrates in my link: Root or water column fertilization?

Thank you for this reference @Dennis Wong , also because I am a big fan of your site and your work.

A lot is clarified when we take the different schools of thought in the hobby into account. Of course there are various methods that all work, some really cheap and straightforward, others less so. I am not referring to just some Osmocote here and there, I also did that, but rather to dedicated substrate soils and additives that need regular supply and resupply. As a hobbyist, I am trying to figure out what is the most economical and sustainable, with evidence of success.

For me, an adjusted EI (I am at about 50%) works just fine, there is enough for all plants, and there is no competition for nutrients between the plants as mentioned on the site. Also, EI does not require water testing, that is the whole point of EI, so on that part I respectfully disagree with the site. I do see, when dosing much leaner there can be a concern for some plants and there may be a need for some extra support through root feeding as I read on the site.

The other argument mentioned on the site, moderating growth rates of individual groups of plants through their root feeding supply, I had not thought of and sounds really interesting.

Perhaps the major weakness of EI water column dosing is that it doesn't create a profitable business, unlike alternatives. Our Japanese friends were smart to see that early enough, I guess, and chose a comprehensive planted tank business model that needed the fancy stuff in the soil.

I am not against root feeding, but just don't see the evidence for doing it when it gets more complicated or expensive than water column dosing. And more to the point of this thread, I find it hard to believe that there is a substantial benefit to the microbes beyond startup, as also mentioned by @ElleDee .

 

[GreggZ]

I have seen several of examples, @GreggZ and others, that inert substrates perform no less than aqua soils, not even to mention all the additives that are for sale. Show me one example where soil supplements were essential in a well dosed tank, I have not seen it yet.

My personal opinion is that the only thing that can be objectively proven is the marketing drive behind soil and soil additives and the cash out for the hobbyist. It's like our own food supplements, for a healthy individual with a healthy diet most of them are not needed whatsoever. But food supplements is a really big market, and many doctors and retailers are in the pocket of this industry. I am using 5 years old AquaSoil, but with next rescape I will invest in an inert substrate that I can use and reuse indefinitely.

I can only speak to my personal experience. Having had both inert and active soils for many years I have experienced very little to no difference. And I've tried root tabs many times over the years, including the ones sold by our friend and saw no difference. But that's just what I have observed in my own tank. Others may experience different results in their tank as each tank is a unique eco system.

In my tank adding active soil, liquid ferts, and root tabs are a waste of money. Now that is relative to my ambitions. I run a large tank mostly loaded with fast growing stem plants with lots of uprooting, and water column dosing works for me. And I can clone any liquid fert on the market for pennies on the dollar, so no interest for me there. Same is true for many other friends of mine who are very well known in the hobby and create beautiful stunning displays.

And while my friend lobbed a veiled criticism at my tank and posted a pic of mine of his site (without asking) to make a point, it doesn't change my thoughts. I am trying to keep up to 30 species happy in one tank. Do I get the absolute peak out of each plant? No but that is not my goal.

My goal is to create a presentation that attracts your eyes and captures your attention. Whether I am successful or not is in the eye of the beholder.

For me, an adjusted EI (I am at about 50%) works just fine, there is enough for all plants, and there is no competition for nutrients between the plants as mentioned on the site. Also, EI does not require water testing, that is the whole point of EI, so on that part I respectfully disagree with the site.

This is an interesting point. I am also puzzled by the suggestions that "EI" style dosing requires more testing. In fact it's the opposite. I front load all macro nutrients and rarely if ever test anything.

In the end all this this talk misses the bigger point. Folks often have nutrient tunnel vision, substrate tunnel vision, root tab tunnel vision, etc. They think that these are the keys to a successful planted tank. They aren't. Get everything else right and you can get by pretty well with a wide variety of parameters. At least that is what I have observed after many years in the hobby.

 

[helpmegrowinganubias]

Hi, I wanted to contribute something. In the past, I had a lot of problems with plants and algae. I contacted @GreggZ and literally told him that I wasn't enjoying my aquarium because of its aesthetics and that it wasn't fun to maintain an ugly tank. I wanted to get into the world of aquascaping. Over the past few months, I've received a lot of help from him (something I'll always be grateful for), but I'll never forget one of the first messages he told me, which basically summed up to saying that if I wanted a beautiful aquarium, I should use CO2. He suggested fertilizing through the water column and explained how he does it (currently, that's the fertilization method I use, and I've seen many others do the same). He also mentioned that I needed to control the light, do maintenance, apply horticultural techniques, and join ScapeCrunch. That message has been like the Ten Commandments for me, and in just a few months, I achieved what I was looking for. Nowadays, my friends and partner are also applying these principles, and they all have successful aquariums, even though some of them have zero knowledge about aquascaping and take a completely practical approach.

In short, what I'm trying to say is that today, people rely too much on technology, which can make us forget the basic aspects of an aquarium. The overabundance of commercial products can cause more problems than benefits. Is using three products for plant nutrition (substrate, fertilizer tablets, and water column fertilization, and in some cases even recommended phytohormones) viable for someone just starting in the hobby and who doesn't even know what nitrates are? Are you also going to tell them that they need to change the water every x days at the beginning because of the aquasoil, that they should bury the fertilizer tablets properly and be careful (I at least ended up with a cloudy tank because a Corydora was attracted to the gelatin coating of the capsules), that they should be cautious when uprooting plants for the same reason and because aquasoil will make the tank a mess if not, that they need to clean the aquasoil in a specific way, that they need to remember to add fertilizer tablets every x months, that the aquasoil will run out in x years, and that they’ll have to sell another kidney to afford it... Personally, that doesn't convince me. Fertilizing with a liquid, changing the water, and siphoning seems like less hassle and allows me to focus on other relevant aspects.

If you've made it this far, thanks for reading, and here’s a picture from someone who hasn't been in the hobby for a year and still doesn't know what pH, nitrates, aquasoil, or any of that is.

 

[GreggZ]

Hey @helpmegrowinganubias thanks for the shout out and it's great to see where your tank is now. You've come a long way and it's nice to see you enjoying your tank again.

Things look like they are going very well. Great mix of healthy looking plants.

Keep up the good work and I look forward to seeing things go from here.

 

[helpmegrowinganubias]

Hey @helpmegrowinganubias thanks for the shout out and it's great to see where your tank is now. You've come a long way and it's nice to see you enjoying your tank again.

Things look like they are going very well. Great mix of healthy looking plants.

Keep up the good work and I look forward to seeing things go from here.

It´s not my tank Gregg, i sold it and i´m out of the hobby. I´m saving for a big tank and make a real dutch! Actually i´m just keeping plants emersed and sharing the stuff i could learn from you and other nice people, also planning my future proyect and continue learning.

 

[GreggZ]

It´s not my tank Gregg, i sold it and i´m out of the hobby. I´m saving for a big tank and make a real dutch! Actually i´m just keeping plants emersed and sharing the stuff i could learn from you and other nice people, also planning my future proyect and continue learning.

Oh yes I recall you mentioned that now. Well tell the person whole tank it is that they are doing a great job!

 

[Tim Harrison]

Great topic for discussion @Art. Microbial communities are essential to healthy and functioning ecosystems especially our aquariums. Not just bacteria, but also other microorganisms such as arbuscular mycorrhizal fungi (AMF). These colonize the roots of numerous aquatic and wetland plants, and form important endosymbiotic relationships.

I'm not a great fan of commercial inoculation products. For one thing they may not contain the species necessary to promote aquarium health. There has been a lot of research on this in recent years, especially with regards nitrogen cycling and it's been found archaea are of equal, if not greater importance than bacteria.

But aside from that bacteria coat every surface on this planet including plants leaves, roots etc. Even in-vitro plants will be covered by latent microbial communities. Given the right conditions these communities will reproduce rapidly.

Bacteria for instance reproduce by binary fission. This response is very rapid, most bacteria have generation times of one to three hours. Some species can double every 20 minutes, given optimal conditions. If that growth rate were sustained, a single cell would give rise to a colony weighing a million kilograms in just 24 hours. However, growth is checked by nutrient availability or accumulation of metabolic wastes etc.

Given those growth rates, even if the supplements contained the right bacteria, they wouldn't really be needed. I've never used them and my tanks usually cycle in about a week, meaning they're habitable for fish and other critters. I think the bacteria usually abundant in gardens has proven to be more beneficial to planted thanks than that found in supplements.

On the subject of N removal from the water column by microbial communities in the sediment. Most occurs at the relatively shallow interface between the part of the rhizosphere that interfaces with the water column. An area known as the oxidized microzone. There will be very little beyond this zone due to lack of water movement and gas exchange.

Macrophyte roots are very leaky structures. This allows them to change the physicochemical environment of sediments through ROL (radial oxygen loss). This along with the secretion of organic chemicals, also through root structures, will increase the abundance and diversity of microbial communities. This in turn also contributes greatly to plant health and the removal of N.

Whilst sediment microbial communities are important for the removal of N, the interaction between plant communities and microbial assemblages in the form of biofilms on roots, leaves and stems also plays a crucial role in N removal and therefore water quality.

Further, a heavily planted deep soil substrate might perhaps allow for a more diverse and abundant microbial community in the rhizosphere which would in turn further benefit the health of macrophytes. And therefore, in turn water quality as plants sequester more N for growth.

And on that subject apparently mycorrhizal interaction enhances the nutrient uptake and protects plants from toxic metals by avoiding their direct entry, presumably by altering membrane transport channels. There is also research that suggests Mycorrhizal networks allow plants to communicate with one another and to share nutrients. An important strategy for dealing with nutrient deficiencies.

I'm not sure continued disturbance, uprooting and replanting, will prevent mature microbial communities from developing, but it may well prevent plants from tapping in to them as a resource. However, there is more than one route to success and good husbandry will undoubtedly go some way to mitigating against this.

Either way, I believe that an established microbial community adds a great deal of stability and robustness to a planted tank, and therefore keeps algae in check. Anecdotally at least, I've had mature systems that have been neglected yet remain in peak health and growth. For instance, where the CO2 has run out, where water changes and fertz dosing have been infrequent to non existent. This scape below is an example...

 

[GreggZ]

Great topic for discussion @Art. Microbial communities are essential to healthy and functioning ecosystems especially our aquariums. Not just bacteria, but also other microorganisms such as arbuscular mycorrhizal fungi (AMF). These colonize the roots of numerous aquatic and wetland plants, and form important endosymbiotic relationships.

I'm not a great fan of commercial inoculation products. For one thing they may not contain the species necessary to promote aquarium health. There has been a lot of research on this in recent years, especially with regards nitrogen cycling and it's been found archaea are of equal, if not greater importance than bacteria.

But aside from that bacteria coat every surface on this planet including plants leaves, roots etc. Even in-vitro plants will be covered by latent microbial communities. Given the right conditions these communities will reproduce rapidly.

Bacteria for instance reproduce by binary fission. This response is very rapid, most bacteria have generation times of one to three hours. Some species can double every 20 minutes, given optimal conditions. If that growth rate were sustained, a single cell would give rise to a colony weighing a million kilograms in just 24 hours. However, growth is checked by nutrient availability or accumulation of metabolic wastes etc.

Given those growth rates, even if the supplements contained the right bacteria, they wouldn't really be needed. I've never used them and my tanks usually cycle in about a week, meaning they're habitable for fish and other critters. I think the bacteria usually abundant in gardens has proven to be more beneficial to planted thanks than that found in supplements.

On the subject of N removal from the water column by microbial communities in the sediment. Most occurs at the relatively shallow interface between the part of the rhizosphere that interfaces with the water column. An area known as the oxidized microzone. There will be very little beyond this zone due to lack of water movement and gas exchange.

Macrophyte roots are very leaky structures. This allows them to change the physicochemical environment of sediments through ROL (radial oxygen loss). This along with the secretion of organic chemicals, also through root structures, will increase the abundance and diversity of microbial communities. This in turn also contributes greatly to plant health and the removal of N.

Whilst sediment microbial communities are important for the removal of N, the interaction between plant communities and microbial assemblages in the form of biofilms on roots, leaves and stems also plays a crucial role in N removal and therefore water quality.

Further, a heavily planted deep soil substrate might perhaps allow for a more diverse and abundant microbial community in the rhizosphere which would in turn further benefit the health of macrophytes. And therefore, in turn water quality as plants sequester more N for growth.

And on that subject apparently mycorrhizal interaction enhances the nutrient uptake and protects plants from toxic metals by avoiding their direct entry, presumably by altering membrane transport channels. There is also research that suggests Mycorrhizal networks allow plants to communicate with one another and to share nutrients. An important strategy for dealing with nutrient deficiencies.

I'm not sure continued disturbance, uprooting and replanting, will prevent mature microbial communities from developing, but it may well prevent plants from tapping in to them as a resource. However, there is more than one route to success and good husbandry will undoubtedly go some way to mitigating against this.

Either way, I believe that an established microbial community adds a great deal of stability and robustness to a planted tank, and therefore keeps algae in check. Anecdotally at least, I've had mature systems that have been neglected yet remain in peak health and growth. For instance, where the CO2 has run out, where water changes and fertz dosing have been infrequent to non existent. This scape below is an example...

View attachment 5812

Wow Tim a lot to digest there and a great post.

I agree that biological maturity is something that is very important in a planted tank.

I've kept very detailed logs of every aspect of my tank for many years. So I can look back in time at any point and match that up to pictures from the same time frame to see how the tank was doing.

In a few cases the tank has had unusual issues. I look back and see that light, fertilization, CO2, flow, maintenance, etc. were all within normal parameters for my tank. When that happens I look to the substrate as a possible issue. Usually doing a thorough cleaning of the substrate rights the ship.

I am guessing this has as much to with the biological activity as with the build up dissolved organics. Not as scientific as your post, and no way to confirm, but I do believe there is a causal effect there and bio health and maturity play a greater role than most suspect.