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Question of the Day Nitrifying bacteria are undesirable in a planted aquarium

Art

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    This is a topic that is currently being discussed in the reefing world. I think it is interesting in the freshwater planted aquarium world also.

    Randy Holmes-Farley says the following. I've made a change from reefing to planted aquariums.

    OK, so the world of [planted aquariums] is loaded with folks talking about nitrifying bacteria as good bacteria, and some other bacteria are bad.

    I think it's a perfectly valid hypothesis that cannot be easily dismissed that nitrifying bacteria are bad for a fully stocked [planted] aquarium.

    Here's the step by step rationale:

    1. [Plants] prefer to take up ammonia instead of nitrate, and will preferentially take ammonia when both are present.

    2. Nitrate requires extra energy to use as a source of N, relative to ammonia.

    3. When nitrifying bacteria are present, they can grab up ammonia present in the water and convert it to nitrate, leaving less ammonia for [plants].

    4. [Plants], seeing inadequate ammonia then need to take up nitrate, causing aquarists to want to raise nitrate above natural levels to ensure [plants] have at least something as a source of N.

    5. Studies show that elevated nitrate can cause detrimental effects on [tank inhabitants] and may not be possible when trying to nitrate-limit the tank.

    Hypothesis: Contrary to popular belief, nitrifying bacteria are undesirable in an operating and fully stocked [planted] aquarium where there are plenty of ammonia consumers.

    What do you think? Should we have smaller filters?
     
    Algae.

    Without that little issue (ha!) we would all use ammonia, or more likely ammonium nitrate.

    I will say that the mega-concentrations that often result from an EI type of mindset bothers me a bit when it comes to the fish. We know that elevated nitrate levels aren't healthy. The real issue in aquariums seems to happen when there's a sudden nutrient shortage. I kinda, sorta think a low-dose steady drip of macros (and micros) would probably suffice.

    Also, whether they're desirable or not, you really can't do much about it. Bacteria will multiply and thrive where and when they can. Even if you solely focus on mechanical filtration, they're going to be there.
     
    Also, whether they're desirable or not, you really can't do much about it. Bacteria will multiply and thrive where and when they can. Even if you solely focus on mechanical filtration, they're going to be there.
    Even if you avoid any filtration, biofilm will form on the glass, substrate,plants, rocks….

    and every body of water in nature and soil that plants live in has plenty of nitrifying bacteria….

    Humans are an interesting lot presuming to know more than God / Nature….
     
    Humans are an interesting lot presuming to know more than God / Nature….
    I think we are pretty good at learning from nature and tweaking it to squeeze out more from this knowledge. I think a good example would be how we breed animals and plants to increase yield or quality. For better or for worse.
     
    As a species we have also been remarkably good at resource depletion and remarkably poor at anticipating unintended consequences…. But your point is taken…
     
    I wonder, what would one do to eliminate nitrifying bacteria that would not harm the fish and plants?
     
    I wonder, what would one do to eliminate nitrifying bacteria that would not harm the fish and plants?
    I’m picturing some perpetual motion water changing machine that slowly drains to a water filter source reservoir, automatically tops off from a RODI tank, and doses fertilizers/buffers via a controller. Could some lunatic please run with that idea?
     
    I’m picturing some perpetual motion water changing machine that slowly drains to a water filter source reservoir, automatically tops off from a RODI tank, and doses fertilizers/buffers via a controller. Could some lunatic please run with that idea?
    You're describing many modern reef tanks today. Automatic water change with auto-top off from RODI reservoir and a controller checking nitrate, alkalinity and calcium and dosing accordingly.

    We just haven't gotten there with planted tanks.
     
    I appreciate everyone's input here. I don't think the idea is to remove nitrifying bacteria as it is everywhere, not just the filter. However, many of us run multiple canister filters with huge media beds for the nitrifying bacteria to be present in great numbers. If we didn't run an intentional biological filter, and this reduce the total amount of nitrifying bacteria, would this slow down the uptake of ammonia by bacteria and leave more for plant uptake?

    A related topic is whether ammonia/ammonium will lead to algae. We know that some people dose ammonium nitrate or urea without causing algae. What's your experience/thoughts about this? Isn't it really tank instability that causes algae, not really ammonia?
     
    Isn't it really tank instability that causes algae, not really ammonia?
    I think it is water that causes Algae. If you remove that you eliminate All algae growth…

    we just need to train the fish to breathe and swim in air….

    So Art, what sort of Ammonia levels would you be comfortable having on a chronic level?

    Many new fishkeepers get frantic with an ammonia spike of 0.5%. My tap water is chronically 1 ppm Ammonia. When I do a 50% water change the tank gets to 0.5%. My ph is around 6.6 so it doesnt bother me and it is gone within 6-8 hours as the beneficial bacteria metabolize it in that time..

    I think the complex expensive systems the reefers use is due to the exacting requirements to keep corals alive…

    I just dont think the freshwater side has the need of that expense and complexity.
     
    @Jhardee85 please stop the insanity I beg you!

    I think it’s inevitable even with a smaller tank based on how we run our substrates and hardscape. You find our real fast when you do a deep clean and notice the bacteria bloom a day later.
     
    If we didn't run an intentional biological filter, and this reduce the total amount of nitrifying bacteria, would this slow down the uptake of ammonia by bacteria and leave more for plant uptake?
    I think that’s a good assumption, I think the fear has always been not being able to control ammonia so having multiple filters and massive amounts of media to combat it. But the reality is, once you reach that state of equilibrium, the plants will be the best filter by absorbing that ammonia. Granted, this will be most effective I think in a CO2 injected tank where plant growth can keep up.
     
    An ammonia spike is an excellent way to get a good crop of algae growing. And by a spike I mean it's introduced into a tank that doesn't have the amount of nitrifying bacteria to process it quickly. If it hangs around it can cause many issues. Have seen it many times when someone loses a fish and doesn't notice it. Or when folks have lot's of decaying plant matter, dirty filters, too many organics, etc.

    As to filtration, I do think filters have some beneficial bacteria in them, but most is located in the substrate, on plants, on the glass.....everywhere.

    Also keep in mind that fish are constantly adding ammonia. So a well stocked tank already has a good steady supply of ammonia.......but a well stocked tank also has a great deal of bacteria that converts it quite quickly.

    All in all there is not much you can do about any of it. At some point there will be equilibrium. The problem is when that equilibrium is disturbed......algae is always lurking and ready to pounce.

    And as to wanting more ammonia in a tank, I know an awful lot of folks who can really grow plants. And not one of them doses ammonia. And very few dose Urea, which is a bit less harsh.

    So no offense to Randy, who I see is quite accomplished in the reef world, but in my experience I have never seen more ammonia to be of any benefit in a planted tank. In fact quite the opposite.

    Of course as usual based on my own experience and what I have observed in successful tanks over many years.
     
    In my experience using urea and ammonia nitrate, they should be very small proportions, but if used by calculator, they burn plants. The calibration of this material is difficult. As for me, if I want to add urea or ammonia nitrate, it must be added only once throughout the week. The rest of the days are phosphate and potassium.
     
    So Art, what sort of Ammonia levels would you be comfortable having on a chronic level?
    Good question but I don't have an answer for you here. I'm just probing this issue. I find that we too often fall into the "that's how we've always done it" mentality and get stuck. Wasn't that the way it was with zero KH?

    I think the fear has always been not being able to control ammonia so having multiple filters and massive amounts of media to combat it.
    Agreed. The filters end up there more for flow than for biological filtration.

    Have seen it many times when someone loses a fish and doesn't notice it. Or when folks have lot's of decaying plant matter, dirty filters, too many organics, etc.
    I agree with you but is this due to the ammonia or the higher dissolved organics? I think we need to get @plantbrain on an experiment. Dose ammonia is a tank with very low dissolved organics. Will it produce algae?
    And as to wanting more ammonia in a tank, I know an awful lot of folks who can really grow plants. And not one of them doses ammonia. And very few dose Urea, which is a bit less harsh.
    This is certainly true. And, I know I'm being 😈 here. I don't mean to imply that you need to dose ammonia to grow plants well. That is clearly not true. However, how do we know if dosing ammonia wouldn't improve even their plant growth?
     
    This is a topic that is currently being discussed in the reefing world. I think it is interesting in the freshwater planted aquarium world also.

    Randy Holmes-Farley says the following. I've made a change from reefing to planted aquariums.



    What do you think? Should we have smaller filters?

    And this is how myths get started, while I respect him and know him from Reef Central, there are several issues with these popular dogmas.


    "1. [Plants] prefer to take up ammonia instead of nitrate, and will preferentially take ammonia when both are present."

    This is bullshit. It's too simplistic as well.
    Diana's book showed a ratio of a % of BOTH NO3 and NH4 25 years ago. It's valid. Concentration also makes a big difference. At low levels, there's going to NH4 produced first from live stock and other organisms. So any that's around can be used by plants or bacteria. NO3 is typically when things are in excess. Only then do you get a build up.

    NH3 is a plant herbicide if you add enough, NO3 is pretty much non Toxic to fish, plants and shrimp over an extremely high range.
    WHERE plants like NH4 and livestock as well? Sediments. It's easy for hobbyist to manage the water column when using ADA AS with NH4 in it.
    as each grain is aerobic on the outside(good for roots generally), inside the grain they are anaerobic, so bacteria cannot attack the NH4 and make NO2/NO3.

    Low levels of NH4 get consumed rapidly. It's hard to trace how much a plant vs the bacteria actually get unless you do 15N stable isotope studies, something I suggested while at UF. Would have made a great research project but I was in a different dept.

    "2. Nitrate requires extra energy to use as a source of N, relative to ammonia."

    Not very much relative to the plant's overall metabolism.
    N limitation is far worse than the extra energy involved regarding growth.

    "3. When nitrifying bacteria are present, they can grab up ammonia present in the water and convert it to nitrate, leaving less ammonia for [plants]."

    Not if the NH4 is in the soil and anaerobic. Also, filters vs plants? Soil/plant surfaces are LOADED with a lot of bacteria, more than the filter in most cases. Filters are just back ups for large slugs of NH4 moving through post large hacks and uprooting etc.

    "4. [Plants], seeing inadequate ammonia then need to take up nitrate, causing aquarists to want to raise nitrate above natural levels to ensure [plants] have at least something as a source of N."

    Ah, total horse manure, what is a natural level? Plants as we all know and have for decades are just dandy with NO3 as the main source of nutrients. A good myth is hard to kill. I'd would hope most folks who have done enough forum for decades would be wiser. Easy to falsify this claim. No ppm for what the NO3 is good or bad, natural or un natural either. 50 ppm? 20 ppm? 10 ppm? 5 ppm? I mean if I'm not adding any, should it not be near undetectable? Plant tanks suck N like no tomorrow.

    "5. Studies show that elevated nitrate can cause detrimental effects on [tank inhabitants] and may not be possible when trying to nitrate-limit the tank."

    WHICH studies and what are these ppm's that have a negative impact and on what specific FW hobbyist fish and Shrimp(a better "canary
    than most fish).

    Hypothesis: Contrary to popular belief, nitrifying bacteria are undesirable in an operating and fully stocked [planted] aquarium where there are plenty of ammonia consumers."

    While I do agree a large bacteria filter in not required, this seems like the old myths from the 1990's.
    Decades ago, Karen mentioned she wants to grow plants, not bacteria. I took that advice and she was correct.
    So I reduced all the mega filtration approaches. Reef folks have done this more or less, but the mega skimmers....we do not have an equivalent. Corals and things like Xenia can strip N out of a reef tank pretty effectively and folks need to dose small amounts of N or feed more, add more livestock to account for it. Reef plants/macro algae also (can)need some supplementation of N as well, KNO3 works well and fish food for the NH4.

    It's not a false dichotomy with N, it's NH4 and NO3. Plants want both. We can see this clearly with water column ferts + NH4 from sediment sources.
    Many of us have dosed NH4 for many years. I do not see it offering near the same impact to growth as soil based sources.
    These are well established observations for decades and many aquarist. If it were true, we would have a much harder time falsifying the claim.
    Testing the % of who gets what, 15NH4 vs 15NO3 etc would answer this question over a broad range of plant species we keep. You could also Use the same method for water column 15NH4 ferts vs bound 15NH4 sources in the soil. And the same for NO3 as well for soil/sediment. Plants/growth/15NH4/15NO3 uptake would be your dependent variables.

    1. I've stated what's wrong(and what is partially right/ or mostly correct)
    2. Offered a method to answer the questions as to who gets what
    3. The relative impact of filter bacteria to plant growth. A certain amount of this is unavoidable.
    4. Showed it's not in line with observed dosing by many folks over long time periods using NO3 and NH4
    5. Does not address soils at all.

    Randy is a smart guy, extremely prolific on line helper, not sure where he got these statements from or if they are even his statements.

    Tom
     
    Good question but I don't have an answer for you here. I'm just probing this issue. I find that we too often fall into the "that's how we've always done it" mentality and get stuck. Wasn't that the way it was with zero KH?


    Agreed. The filters end up there more for flow than for biological filtration.


    I agree with you but is this due to the ammonia or the higher dissolved organics? I think we need to get @plantbrain on an experiment. Dose ammonia is a tank with very low dissolved organics. Will it produce algae?

    This is certainly true. And, I know I'm being 😈 here. I don't mean to imply that you need to dose ammonia to grow plants well. That is clearly not true. However, how do we know if dosing ammonia wouldn't improve even their plant growth?

    0.8 ppm was the assumption based on daily uptake for NH4. This NO3 equivalent is roughly 3-4 ppm as NO3.
    I'm sure some tanks would consume more. A strong to moderately N limited tank would likely suck out a lot more the 1st 1-2 days. Then level off. Still, it would be unlikely many tanks would need MORE than this daily assumed rate. But it might limit growth for some really weedy species. Most well run high energy tanks would not need more than this with ADA AS. the residual overall average level of NH4 floating around is what would determine bacteria CFU's density. So if you dose daily 0.8 ppm and plants suck up most of it, does not matter.

    This is a big assumption to think bacteria will get it before the plants, I think they may get a little certainly.........but the plants are often better at higher ppms. Same for algae(small surface to volume ration and demand for N).

    Not that I can say as far as low or high DOC's and NH4 dosing or with doing no water changes on a new tank with ADA AS version 1.
    Would have been nice if it was that simple.


    As far as dosing NH4, Ammonium sulfate was the preferred salt for this. You could try NH4NO3 also. I recharged some old ADA AS using the (NH4)2SO4 at 2 tables spoons per liter recently. Seem to work about 1/2 as well as new ADA AS. Soem fairly obvious reasons why that is.

    Water column I've used it for years, but there's little evidence it's better, unless you subscribe to belief and not evidence.
    Location of the NH4 is a key factor. While many plants might not have a foliar preference, in the root zones, I would suggest they do.
    We do see improved growth with ADA As and similar products. The product with the rich NH4 has the best growth clearly.

    You can think about plant growth and N from ferts dosed or from the soil that's reasonably enriched with N like the figure below. Both work, but both together are even better as far yield. Now some fool will come along as say "well, my plants grow fine without any ferts(cough cough, who could THAT be? haha)" which is true and the slower growth might be preferred with some tanks/species, habits. Likely wise, some might be fine with only water column ferts. Generally though, the figure has a specific goal, max yields which shows preferences and the best growth rate. I cannot pick out some fool's end goal for every claim that comes along, it's too arbitrary. Still, for many, they want to slow things down, Reduction or removal of ferts in the water and not in the soil is a pretty good idea.
     

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