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Thread: Aquatic Plants' Preference For Ammonia

  1. #1
    Daihonmei MikeM's Avatar
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    Aquatic Plants' Preference For Ammonia

    Regulars on this board will be bored to hear me say that the algae and plants in our ponds prefer ammonia as a nitrogen source over nitrate. I have said it so many times. However, an otherwise knowledgeable person stated the contrary on another board recently and, checking around the internet, I find a lot of misstatements not only by hobbyists, but by several highly regarded suppliers of pond products and equipment. The common story line is that through nitrification the ammonia released by our koi (and decomposing wastes) is converted to nitrite, which is converted to nitrate, with the nitrate being consumed by algae and plants. This is a very misleading story line. The truth established by numerous scientific studies is that aquatic plants compete with nitrifying bacteria to consume ammonia. Nitrate is used by aquatic plants to an appreciable extent only when ammonia is so low that plants cannot meet their nitrogen needs. This is quite different from terrestrial plants, which rely almost solely on their root systems to obtain nutrients. Nitrate is preferred by terrestrial plants (as a general rule). Aquatic plants are able to absorb ammonia through their leaf and stem surfaces, making the entire exposed surface of the plant (or algae filament) an organ for consuming nutrient.

    Among the numerous studies is one that used the common aquatic garden plant Elodea (Anacharis in the trade). Placed in water with equal parts of nitrate and ammonia/ammonium, within just 16 hours the ammonia level was lowered by 75%, while nitrate remained stable.... until ammonia was greatly lowered, at which point nitrate consumption commenced at a much slower rate. These study results have been repeated with innumerable aquatic plants commonly grown in ponds and aquaria.

    An interesting aspect of utilizing ammonia as a nitrogen source is that the plants consume ammonia in the absence of light at virtually the same rate as they do when in optimal light. In comparison, nitrate utilization drops 60-70% or more in the absence of light. While the reason for this is subject to debate, it very likely relates to a basic fact. When nitrate is used as a nitrogen source, the initial step in metabolizing it is to convert it to ammonium. This process requires energy, and a lot of it. Aquatic plants skip this energy robbing step by consuming ammonia directly. In the absence of light, aquatic plants have a hard time using nitrate. They can use ammonia/ammonium, continuing to grow in a less interrupted fashion. .... You say that algae in your pond seemed to have grown overnight? Well, it did. Using stored sugars and available ammonia for growth, rather than metabolizing nitrate, growth can occur in the dark (until reserves are depleted, of course).

    The misinformation that circulates can have an adverse impact on our koi, if somebody gets the idea that they can rely on plants and do not need to perform water changes. The bigger harm is to the wallet of the hobbyist who relies on the misinformation in making useless expenditures thinking they are doing something good for their koi. And, the hobbyist can end up engaging in useless work that frustrates when desired results are not obtained. If the manufacturer of a product asserts inaccurate information in marketing their product, perhaps that product will not accomplish what the advertisement promotes.

  2. #2
    MCA
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    Honmei MCA's Avatar
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    Few things do more for our ponds that a simple, good old fashioned, major water change. That of course the source water is worth having. Leave plants to the water gardeners who are not part of the core koi keeping hobby.


    Another elitest koi keeper who does not mistake water gardening for koi keeping.

  3. #3
    Tosai
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    "The truth established by numerous scientific studies is that aquatic plants compete with nitrifying bacteria to consume ammonia. Nitrate is used by aquatic plants to an appreciable extent only when ammonia is so low that plants cannot meet their nitrogen needs." Quoted from above post.

    Mike, I've always pondered how to know when filters become fully charged and mature around this time of the season so that I know when to ramp up my feeding. After you've said this I may have stumbled upon an answer for my pond. During the past several weeks I've had small amounts of nitrates. Recently it is reading zero. Would it be right to say that the nitrifying bacteria in my filters are now at full strength, that my ammonia level is now so low, the surface algae covering my pond resorted to consuming my nitrates?

  4. #4
    Daihonmei MikeM's Avatar
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    That is an interesting theory. Some questions: (1) Have you kept track of ammonia levels so you can say whether ammonia is lower now than several weeks ago? ...A very sensitive test kit might well be required to detect ammonia levels which are below the detectable level of the test kits generally available. (2) Have you performed water changes that would explain the decrease in nitrate levels detected? (3) Have organic inputs to the pond changed during this period?... Springtime pollen, etc. a few weeks ago and none currently? ...Change in type of food being fed? Other? (4) Has your source water nitrate level changed?... Changes in rainfall, snow-melt, etc. can have seasonal effects on nitrate in tap and well water.

    Depending on your answers to these questions, if you are observing a lowering of nitrate and algae growth with water changes remaining constant, it would seem possible that your theory is the explanation. In any event, if you have no detectable ammonia or nitrite, and the nitrate level is going down, it certainly seems like it is time to increase feeding.

  5. #5
    Sansai Reza's Avatar
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    Using plants in koi ponds are depended on hobbyist's personal manner. As MCA said some koi keepers are interest in water gardening and some others not.
    But using plants in pond has its own Cons and Pros. I am interested in koi keeping in Japanese style and water gardens, but my brother loves koi keeping in desert like ponds. In other hand some plants like water hyacinth, are very useful for water treatment :

    wikiperdia:

    The roots of Eichhornia crassipes naturally absorb pollutants, including lead, mercury, and strontium-90, as well as some organic compounds believed to be carcinogenic, in concentrations 10,000 times that in the surrounding water. Water hyacinths can be cultivated for waste water treatment.

    Water hyacinth is reported for its efficiency to remove about 60–80 % nitrogen (Fox et al. 2008) and about 69% of potassium from water (Zhou et al. 2007). The roots of water hyacinth were found to remove particulate matter and nitrogen in a natural shallow eutrophicated wetland (Billore et al. 1998).

    In other study in hospital wast water treatment by artificial lagoon methods and using aquatic plants succeed to remove to +99% nitrate from water.

  6. #6
    MCA
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    As MCA said some koi keepers are interest in water gardening and some others not.
    And those are two distinctive hobbies. A purpose built koi pond is not a water garden and vice versa. Form follows function. I can park a motorcycle in the living room of the house. That does not make the living room into a purpose built garage.

    I have done both hobbies in parallel years ago when we lived in Plano TX. But in my retirement years, I stick with koi keeping. I want my plants outside the pond and all looking like a Japanese garden.

  7. #7
    Oyagoi yerrag's Avatar
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    An interesting aspect of utilizing ammonia as a nitrogen source is that the plants consume ammonia in the absence of light at virtually the same rate as they do when in optimal light.
    Mike, I'm not sure how this could be. In the absence of light, the plants would not be able to carry out photosynthesis. And with light, they could. I would think that as a result of less photosynthetic activity, the plants would not be consuming as much ammonia as well. However, there may be other processes in the plant while it is at rest (not exposed to light) that would require the use of ammonia. And if the rate of ammonia consumption is as strong while the plant is at rest, then that might explain the constant ammonia consumption thru night and day.

    At any rate, I welcome the idea that plants would prefer to consume ammonia over nitrate. And that the ammonia consumption is constant thru night and day. I like to have plants in my biofilter (mine is anoxic) as I really felt my nitrate is much lower with plants. The plants alone will not consume all the ammonia production of my pond's koi, but it will help lower the nitrate as there is less nitrate produced from the portion of ammonia it keeps from going through the nitrification cycle and producing nitrates.

    The danger with plants is that it is a very reliable source of parasites. I won't take any chances in skipping the quarantine and treatment of plants so as to prevent parasites from being introduced to my pond. I do not like plant or vegetable filters for their tendency to accumulate debris that becomes a source of pathogenic bacteria, but I welcome using plants whose roots grow in the bcb (bioscenosis baskets) that form my anoxic system. I find that as long as the plants are manageable, I can get to remove the rot of dead plant leaves regularly to keep them from accumulating. With such a setup, the plants enhance the performance of my anoxic filter.

  8. #8
    Daihonmei MikeM's Avatar
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    Quote Originally Posted by yerrag View Post
    Mike, I'm not sure how this could be. In the absence of light, the plants would not be able to carry out photosynthesis. And with light, they could. I would think that as a result of less photosynthetic activity, the plants would not be consuming as much ammonia as well. However, there may be other processes in the plant while it is at rest (not exposed to light) that would require the use of ammonia. And if the rate of ammonia consumption is as strong while the plant is at rest, then that might explain the constant ammonia consumption thru night and day.
    Yerrag: You are overlooking the purpose of photosynthesis. Photosynthesis is a process used to convert light energy into chemical energy. The chemical energy is stored in carbohydrate molecules, such as sugars. These are synthesized from carbon dioxide and water, with oxygen being produced as a waste. The energy thus stored can be released later to fuel the plant's growth. Their growth requires nitrogen and other elements, plus energy obtained from sugars previously created through photosynthesis. Plants need light to engage in photosynthesis, but do not need light to grow... as long as sugars stored during the day are available.

  9. #9
    Oyagoi yerrag's Avatar
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    Quote Originally Posted by MikeM View Post
    Yerrag: You are overlooking the purpose of photosynthesis. Photosynthesis is a process used to convert light energy into chemical energy. The chemical energy is stored in carbohydrate molecules, such as sugars. These are synthesized from carbon dioxide and water, with oxygen being produced as a waste. The energy thus stored can be released later to fuel the plant's growth. Their growth requires nitrogen and other elements, plus energy obtained from sugars previously created through photosynthesis. Plants need light to engage in photosynthesis, but do not need light to grow... as long as sugars stored during the day are available.
    Good points Mike. That explains why ammonia is consumed by plants at night for its growth. During daytime, when there is daylight, where is the ammonia used for? Is it also for growth, or is it needed also for photosynthesis? Or for other processes?

  10. #10
    Daihonmei MikeM's Avatar
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    There is no material difference between night and day in the use of nitrogen. Nitrogen is not directly a part of the photosynthesis equation, but is essential for chlorophyll. So, yes, nitrogen is necessary for photosynthesis to occur. It is also an essential component of amino acids, the basic building blocks. So, it is crucial for innumerable functions.

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