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Alternative Nitrate Reduction via Emergents


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I had the good fortune of having limited access to an ichthyologist and marine biologist who operate an LFS here in Southern California and work at an aquarium in San Diego. We began what became almost a full year of informal but largely quantified gatherings of data on nitrate reduction techniques and efficacy for freshwater aquariums. Some is unfortunately anecdotal but much of it was quantified in a way that some Aquarists may find helpful.

Filtration options for nitrate reduction, can be difficult, expensive and surprisingly fragile. The aerobic bacteria consume ammonia and nitrite, the anaerobic consume nitrates...but the latter are fussy eaters!

Nitrate reduction via filtration often has little to no effect as it can take 6-8 months to build a sufficient anaerobic colony to actually reduce nitrates meaningfully...and this requires enormous volumes of media.

Far more than would be need for the rest of the nitrogen cycle!

We began cultivating anaerobic colonies in pond media and found the amount of media required for an efficacious anaerobic colony to be far greater than would be practical in most instances. Nitrate reduction via anaerobic colony filtration is VERY inefficient and requires voluminous amounts of media for meaningful nitrate reduction.

One example being a massive 900gph canister filter with some 6L of media capacity and TWO of these filters with a total of 12L of media, still cannot support enough media for effective anaerobic colonies for a ‘typically stocked 125G SA cichlid tank’ for significant nitrate reduction.

Despite the deliberate architecture of this media (BioHome and Pond Matrix) to favor anaerobic colonization, anaerobic bacteria require a slower flow to maintain an oxygen-free environment. To that end the flow rates were rheostatic-ally altered as we found the greatest growth rate of anaerobes to be circa 50GPH. 

One such filter has ample amounts of flow and media capacity for aerobic colonies (the bacteria that removes ammonia and nitrite), but for anaerobic colonies (the bacteria that consumes nitrates), you’d need FOUR such canisters (25L pond media or similar) to have enough media to reduce nitrates just 10PPM!

This "Catch 22" inefficiency is compounded by the reduced flow rate such that nitrate reduction via media is very inefficient.

In addition, we also found that the anaerobic colonies are MUCH more fragile than aerobic such that they are easily killed by accident. I cannot quantify this section but I have experienced the results and I’ve yet to successfully neutralize rechargable media (with bleach) well enough to NOT reduce the anaerobic colony count.

In fact, re-using rechargable (with bleach) media that was then soaked in dechlorinator for 24 hours still killed off almost 6 out of 8 months growth of the anaerobic colony! Yet the aerobic bacteria saw no drop in population.

(I believe "Pond Guru" mentions similar results in one of his videos.)

I went a different route after months of trying to get meaningful nitrate reduction in the filters. Instead of trying to get nitrate reduction with more filters or additional media, I tried Epipremnum/riparian plants: roots in the water, leaves out the top.

I replaced part of the glass with plastic lighting grid to support the roots and stalks:

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One tank was a 120G (left) heavily stocked with adult, SA cichlids, 12 Acaras, 2 large plecos and 8 Severums in this case:
 

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A 2nd tank, a 125G (left) was heavily stocked with larger fishes, plecos, Oscars and pacu’s (I’ve since had to rehome my beloved pacu’s as they were approaching 18″ in length!):

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120G - 125G


The following are before and after a two week period with Epipremnum/riparian plants above in these tanks:

-The 120 typically reached circa 40ppm after a week when I’d do a WC.

-Inside of two weeks, the 120G at 40ppm has yet to ever reach 10ppm.

                                                                 *
-The 125 was more problematic with nitrates I was having enormous difficulty controlling. This tank (prior to rehoming the pacu’s) would typically reach 80ppm-160ppm inside of 1 week (!) such that I was performing 2-3 WC’s/week until I could rehome them!

-Same time frame, the circa 80ppm-160ppm tank had still not risen to even 30ppm!


There was also little question that the nitrates fell further still once we installed grow lights. This is not shown in the pictures as they were not installed yet;

-With the lights on 12-16 hours/day or so, the 120 dropped from 10ppm to 5ppm, or possibly 0, it’s that difficult to read.

-The 125 dropped to 10ppm and has yet to ever reach 20ppm since adding the grow lights.


There are two properties to be mindful of in play and it’s entirely photosynthetic. Terrestrial plants use more nitrates vs ammonia than aquatic plants due to the availability of greater photosynthetic energy. They evolved with leaves under the sun, and in turn, enjoy more light energy which allows them to directly process nitrates more efficiently. Aquatic plants first absorb ammonia and will attempt to expend more energy if need be photosynthetically to consume nitrates so long as enough light energy is present.

The latter is more efficacious when the lighting is stronger which is not optimal for most aquatic plants nor the fish as the efficacy of nitrate consumption is quite related to the amount of light the plants are exposed to. Naturally, submerged plants would see diminished light and evolve accordingly. But terrestrial plants evolved for this environment.

Specifically, there is a difference between aquatic and terrestrial plants in nitrate assimilation and it's largely spectral.

*** I've placed that data at the end of this piece as it's chemistry and some may find it tedious.

I used pothos and monstera in my tanks as well as Lucky Bamboo in a 3rd tank. A single, $20 pothos plant has virtually eliminated nitrates in the 120 and the same with the 125 since rehoming the pacu’s:
 

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The big (literally and numerically) surprise was the dracaena or Lucky Bamboo. The pothos revealed its full potential in under 2 weeks. Lucky Bamboo took longer to display results, about 4 weeks vs only 2 weeks for pothos, but the 'bamboo' in particular has reduced nitrates so greatly, I’m not confident I can measure any at all with a liquid test kit now:
 

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In my disbelief, I went out and bought a fresh liquid test kit to see if mine had spoiled but again, NO nitrates! A fully stocked SA cichlid tank with 0 nitrates? It sounded crazy to me but of all of the plants I’ve tried, Lucky Bamboo is the nitrate eating champion thus far.

(What this older image does not show is their growth. In case you were wondering where all those nitrates went, the Lucky Bamboo has grown from 24" stalks to now 6' in height!)
 

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I don't bother with rooting cuttings. I just wash the roots and let them drape into the tank through the plastic lighting grid. Of all my fishes, only the Severums eat the roots (and the plecos eat the algae on the roots).

NOTE on Pothos Toxicity:

We also tested the pothos et al for toxins leaching into the water column. It does not do so at any PH that would allow fish to survive. Additionally, we describe how you can test for pothos (and others) toxins yourself with very inexpensive and commonly available home urinalysis test strips. I'll post this test next as pothos toxicity is understandably a common concern for people considering emergent plants in their tanks. 

I have seen my Severums eat the pothos roots for over two years without incident:

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While it may not appeal to everyone, a single Epipremnum/riparian plant can remove virtually all the nitrates directly from the water column if given enough time (weeks).

I wish this could be more extensive and exhaustive and less anecdotal but given the limitations of our testing, one thing I can say with confidence, is there's no greater nitrate reduction one can get for a freshwater tank for $20!

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Many thanks to OnlyGenusCaps for his guidance!

 

*** The Physics Behind Aquatic and Terrestrial Plants Nitrate Assimilation:

What nutrients a plant assimilates, ammonia to ammonium or nitrates directly, is of course species-based but largely, it's wavelength based.

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Terrestrial plants will typically see more red and white light whereas submerged plants not only see subdued white light (relatively), they see a spectral change towards blue which will exhibit much less photosynthetic energy than red such that the plant may not have the available energy to directly consume nitrates and will instead convert ammonia to ammonium.

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The ammonia/ammonium conversion requires much less energy which is but one reason aquatic plants tend to favor ammonia vs nitrates. This further compounded by the fact that ammonium is a cation and nitrate is an anion so ammonia is more readily processed by this metric as well as this is merely a stage of the entirety of the photosynthetic cycle (direct assimilation of ammonia by plants is caused by insufficient light energy). In aquatic plants, it only need add an ion (a charge) to create ammonium as opposed to the far greater energy required to assimilate nitrate itself (as the charged compound will innately contain additional energy to continue the process). 

The environmental reason however is largely spectral. The wavelengths that power nitrate consumption reach peak efficacy at about 660nm, Red, or optimal efficacy for chlorophyll and phytochromes (below is such an example but it focuses on green light absorption).

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Blue light too can power nitrate consumption but it is subdued by water penetration AND in that in concert with the shorter wavelengths and the ionic charges, it is much less efficient in processing nitrates as they require more energy for reduction as opposed to the simple conversion of ammonia to ammonium as aquatic plants do.

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This chart shows how a plant assimilates nitrates in the first 48 hours of absorption from any given moment. It demonstrates how a submerged plant in subdued and/or bluer light cannot uptake nitrates as efficiently as terrestrial plants under red or white light. The aquatic plant eventually catches up with nitrate assimilation in about 48 hours.  

The red circled area indicates the actual cation, the point where the plant assimilates ammonia to create ammonium!

This process is temporally but entirely bypassed by the terrestrials, direct to nitrate.  

To that end, with brighter, whiter light and a touch of evolution, it's little wonder why floating plants are commonly called "nitrate sinks"!  Perhaps it's only of interest to an old physicist but it is the last chart excites me the most!

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The old Hindu edict; "Many Paths to the Same Summit" is certainly true here. 

 

In inverse order of efficacy in nitrate reduction; be it filter media (anaerobically), aquatic plants or terrestrials , if given enough space, time and quantity, all of these can remove nitrates to similar levels. But their efficacy is very different as they will favor ammonia or nitrate and this changes over time and with the light quality.

All told, it's a lot easier for most of us to remove nitrates with plants than filters!

                                                                          *

UPDATE:

@OnlyGenusCaps made an interesting and important point and allowed me to quote him below.  Essentially, that although you can bias a plant towards the consumption of nitrate, ammonia or ammonium with different spectra, it's not necessarily good for the plant!

Here is his quote:

@OnlyGenusCaps: "There is a big misconception, even among those who work on LED lighting about the importance of matching spectra to absorbance peaks. The problem is it is all an engineer's approach to biology that fails to capture the plasticity of living systems.  The "blurple" grow lights are a manifestation of this.  The idea is if you match the absorbance peaks of chlorophylls you will minimize the light energy you need to produce and maximize the energy proportion the plant can use.  That's all well and good in concept, but plants have myriad antenna pigments they use to harvest other wavelengths, and they gain information from these.  These are the colors people see in the autumn on deciduous trees.  So, you are totally correct that full spectrum is now being recognized as better for plant growth and health.  The best research LED grow light tout matching sunlight as closely as possible.  Turns out plants aren't just machines that you can more efficiently plug energy into to get better output.  They are living, complex organisms.  That's what make it all so much fun!!!"

The chart below (I love charts) further illustrates his points. Each stage in the photosynthetic process, does indeed accomplish varying goals for the plant. For example, stomata regulation is largely accomplished by blue light yet red light enjoys the lion's share of CO2 assimilation. That is, the entire spectrum has photosynthetic tasks that overlap but potentiate with specific light color and intensities. To that end, while you can bias a given plant's assimilation with lighting color, red/nitrate, yellow-green/ammonium, blue/ammonia, white is still best for the plant itself:

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Edited by dasaltemelosguy
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I absolutely love this! Thank you, @dasaltemelosguy! I am looking at canisters for mechanical filtration, in tank plants for biological filtration, and yes, Pothos and nitrogen hogs for additional waste processing! Oddly enough, I am finding these same principles applicable to saltwater tanks! Looking at a weird addition of mangroves in a "brackish side step" to my V-Sump.

Thank you so much for posting this!

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Thank you. This was fantastic. I use pothos in all my tanks now in the plastic egg crate inspired by you awhile ago. I have been eyeing lucky bamboo for a few months but was afraid I would lose too much nitrate consumption by switching out the pothos. I was never convinced enough on the nitrate home media to try it so it’s good to know I’m not missing out. 

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First off, this is excellent for so many reasons! 

To begin with, I've been speaking to some folks at the local aquarium club about the possibility of providing small grants to help members do their own research, and then present it to the club (and perhaps more widely).  This will be the example I will use to sell the concept.  It is the gold standard I have run across for this scale of work.  Well done!!!

Also, that Dracaena braunii, a.k.a. "lucky bambo", frankly, just looks awesome in that tank.  The impacts on nitrogenous wastes aside. 

Lastly, I began interacting on fish forums a bit over a year ago because I was hoping to hash out with folks which FW plants might make for the best refugium on a sump design.  I failed in that first effort for a variety of reasons.  I was lucky I found two good people to talk to about it (one of whom directed me to this forum, and I've not looked back), and they completely changed how I view the format of sumps.  But for the refugium piece, I've never had a thorough test available for any of the things I've been able to discuss in concept.  And here, you have set it all out before me.  Done the work.  And made it accessible.  I can't tank you enough!  You have once again changed my entire paradigm about optimizing a sump.  I'm redesigning my sump (this project has taken for-ev-er!) to include a place for terrestrial plants rather than a submerged refugium system like in SW sumps, entirely based on the merits of your presentation here.

Thank you for sharing your results!

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I might need an "Explain it like I'm 5" for this one...but if I'm reading this correctly, the most effective setup for processing nitrates would be terrestrial plants (pothos or lucky bamboo in this case) grown with their roots in the water, blasted with white and red spectrum light?

Is that pretty much the long and short of it?

(I only ask because I'm at a bit of a crossroads with my own refugium project where I'm not necessarily seeing the results I was initially hoping for and my sump system is precarious at best. So something that I wasn't constantly worrying about flooding my living room would definitely be worth exploring)

Edited by B1gJ4k3
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@B1gJ4k3 I use pothos, peace lilly, lucky bamboo, areca palm and other plants in my setups and they make maintenance a breeze, I easily go a month and often more without needing to do a water change. I do not use a refugium (my filtration is just a sponge filter(s)) but rather let the plants grow above the water line of the display tank with overhead lighting. They remove the nitrates, provide shade which minimizes algae growth and help the fish feel safe, and they add beauty to the aquariums. I would highly recommend it to anyone looking for a healthy low maintenance aquarium. 

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On 11/8/2021 at 7:31 PM, B1gJ4k3 said:

I might need an "Explain it like I'm 5" for this one...but if I'm reading this correctly, the most effective setup for processing nitrates would be terrestrial plants (pothos or lucky bamboo in this case) grown with their roots in the water, blasted with white and red spectrum light?

Is that pretty much the long and short of it?

(I only ask because I'm at a bit of a crossroads with my own refugium project where I'm not necessarily seeing the results I was initially hoping for and my sump system is precarious at best. So something that I wasn't constantly worrying about flooding my living room would definitely be worth exploring)

No need, you understood it perfectly. You're spot on. Not that our tests were exhaustive but of these plants: Pothos, Monstera, Peace lily, Lucky Bamboo and Anthurium, the Lucky Bamboo used the most nitrates and the peace lily, the least. My suspicion on the latter being it is outcompeted by the other plants. I just read about your refugium project and it sounds frankly, awesome. I may copy your idea! In any event, yes, the Lucky Bamboo under red light will use the most nitrates. White light if bright enough, will do the same but adds some blue which is needed for ammonification if desired. 

On 11/7/2021 at 5:58 PM, eatyourpeas said:

I absolutely love this! Thank you, @dasaltemelosguy! I am looking at canisters for mechanical filtration, in tank plants for biological filtration, and yes, Pothos and nitrogen hogs for additional waste processing! Oddly enough, I am finding these same principles applicable to saltwater tanks! Looking at a weird addition of mangroves in a "brackish side step" to my V-Sump.

Thank you so much for posting this!

Thank you so much for the very kind words. I was lucky in that the LFS owners gave us lab access so we were finally able to attach numerical values to real world results.  I'd love to hear more about your saltwater findings. In particular I had always wondered about mangroves. Thanks again. 

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On 11/8/2021 at 6:58 PM, OnlyGenusCaps said:

First off, this is excellent for so many reasons! 

To begin with, I've been speaking to some folks at the local aquarium club about the possibility of providing small grants to help members do their own research, and then present it to the club (and perhaps more widely).  This will be the example I will use to sell the concept.  It is the gold standard I have run across for this scale of work.  Well done!!!

Also, that Dracaena braunii, a.k.a. "lucky bambo", frankly, just looks awesome in that tank.  The impacts on nitrogenous wastes aside. 

Lastly, I began interacting on fish forums a bit over a year ago because I was hoping to hash out with folks which FW plants might make for the best refugium on a sump design.  I failed in that first effort for a variety of reasons.  I was lucky I found two good people to talk to about it (one of whom directed me to this forum, and I've not looked back), and they completely changed how I view the format of sumps.  But for the refugium piece, I've never had a thorough test available for any of the things I've been able to discuss in concept.  And here, you have set it all out before me.  Done the work.  And made it accessible.  I can't tank you enough!  You have once again changed my entire paradigm about optimizing a sump.  I'm redesigning my sump (this project has taken for-ev-er!) to include a place for terrestrial plants rather than a submerged refugium system like in SW sumps, entirely based on the merits of your presentation here.

Thank you for sharing your results!

Thank you so much! I'm so happy some people are finding the findings of value! I love your idea of sponsored research! I never thought of that but with some inexpensive equipment and educated volunteers, there's infinite potential! 

I'm very interested in the sump idea. That would allow for much more control and efficacy than what I did on top. Guess we gotta watch for bamboo sales!

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On 11/7/2021 at 8:30 PM, Isaac M said:

@AndEEss in my experience it does grow roots at the base but they are not very substantial. More like that of an aquatic stem plant rather than a sword plant or crypt. 

Exactly. One of my parrots dug one up and after 3 months, the roots are still seem no larger but the plant is now 6' tall! Go figure!

 lbr_.jpg.27ceff22c1dedb517629e727f9a811f3.jpg

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On 11/7/2021 at 11:08 PM, Guppysnail said:

Thank you. This was fantastic. I use pothos in all my tanks now in the plastic egg crate inspired by you awhile ago. I have been eyeing lucky bamboo for a few months but was afraid I would lose too much nitrate consumption by switching out the pothos. I was never convinced enough on the nitrate home media to try it so it’s good to know I’m not missing out. 

Thank you so much for the very kind words. I too wondered about the bamboo's efficacy until we tested it as it's not all that green and is not a fast grower, imperfect signs of high nitrate eaters. I can't explain why the bamboo took twice the time to potentiate over the pothos but eventually it prevailed. The only caveat I see being my latest "grove" grew 3' taller in 3 months! I may need a skylight!

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@dasaltemelosguy Thank you so much for this!  I’m so glad you’ve done all this testing and laid out your findings so well.  Your tank inspired me months ago and now your research inspires me further!

I’m finding my lucky bamboo growing faster than I expected and I would love to see pics of your super tall bamboo!

Here is a pic of my bamboo tops at the beginning just a few months ago (July 26) and then one tonight.

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Plus the difference in the pothos and peace lily.

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@dasaltemelosguy or anyone, OK, I went to my local Walmart (live in a small town, not too many choices) and found some lucky bamboo, I cut a piece of the egg crate plastic to fit the back of my aquarium so now what?  I separated the bamboo stalks-there are 5 of them-they are a little big to fit through the 1/2 in squares of the egg crate-do you just squish them down in there or cut bigger holes in the egg crate?  Do I leave the existing roots or cut them off and let them grow new "water roots"? I really wanted some pothos, but couldn't find any. I'm really excited about this!

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What I did was when the stalks or plants were too large for a single hole, I didn't want to force them so I twisted out the little partitions to make the holes wider. A tight grip with a pliers and a bit of wiggling and they snap right out.

I remove the 4 in the circle for a larger opening:

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Also as they grow, you may need to snap 2 or 4 more out to accommodate their growth. My anthurium fattened up so greatly, I had open one to 4 x 4 holes in size! 

When I snap out the little partitions, I put a net under it should and fragments shatter. Also a single hacksaw blade fits in one hole to score them or saw them out too.

 

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This is such a great experiment, laid out well making it reasonably easy to follow. This absolutely cements that I will be using lucky bamboo and pothos.

Is it required to start with lucky bamboo that goes from planted at bottom to out of tank at top? The tank I wanna use is 25” tall so I would need to start with a 30” piece?

On 11/8/2021 at 9:58 PM, OnlyGenusCaps said:

I've been speaking to some folks at the local aquarium club about the possibility of providing small grants to help members do their own research, and then present it to the club (and perhaps more widely)

Awesome idea! Really will help promote a more educational approach to this hobby.

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I know, OnlyGenusCaps has an inspired idea there. I know I'm going to ask the people who helped with the tests about it next I see them. 

One of my tanks is 25" also. The bamboo with the curl on top doesn't quite fit so you may want to find straight stalks. I bought 32" stalks but with the curl, it doesn't quite reach past it. 

I don't know if they actually need to be planted. We did so and I assume the detritus in the gravel helps them grow but in truth, I don't really know. They are typically sold to be kept in water in a bowl or vase with periodic additives of nutrients so perhaps the roots do not need planting? 

If anyone knows, I'd be very curious myself. They are insanely hardy but if the leaves lie in the water, they will rot. So long as the leaves have air, they seem to start getting taller after about a month. 

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On 11/7/2021 at 4:54 PM, dasaltemelosguy said:

I wish this could be more extensive and exhaustive and less anecdotal but given the limitations of our testing, one thing I can say with confidence, is there's no greater nitrate reduction one can get for a freshwater tank for $20!

It’s good you have access to a great group to do some crowd sourced testing. 😀I have a tank in mind already! 

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