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Thread: Nitrate limitation.

  1. #11
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    The first 2 years I setup my 75G I was getting 0.00 readings on my $200 Hanna Phosphate meter... even went so far as to have a fellow reefer bring his same meter over to test to verify because no one could believe my system could have that reading. Since that time though it has been a constant battle as things have been skewed in my tank.

    I don't agree that you can't remove more N than P or more P than N, that is easily proven to be false. Anyone can put a ton of GFO in a system that has high nitrates and phosphates and skew the parameters that way. That same thinking goes the other direction in terms of bacteria. Bacteria seem to either follow the redfield ratio closely OR they remove more nitrates than phosphates (in anaerobic areas), but as far as I know, there isn't a bacteria strain that consumes more phosphates than nitrates for our hobby (there are strains that are used for wastewater treatment that do consume more Phosphates than Nitrates), meaning if all things are equal, algae and bacteria, most systems will likely skew towards a phosphate problem over time because even in barebottom systems there are anaerobic areas within live rock for denitrification bacteria to colonize. This can happen fairly quickly (in reef terms, 2 years on my system) or can take decades, it all depends on the tank setup.

    Your analogy of a sealed room is a little flawed. I can't even think of how that analogy applies here. To me, that analogy is more like saying "I have a 100G tank with 5.0 phosphates and 200 nitrates, but when I dump my entire 100G of dirty water into the ocean, it doesn't seem to have any effect on the parameters in the ocean". That is the same as removing just the O2 from a room, leaving CO2 and the other gasses, then opening a door. The sheer volume of "air" on the outside vs inside will quickly equalize the air inside when the door is opened... but I don't see how that relates to phosphates/nitrates and adding food to a system. If I have a system with .1 phosphates and 0 nitrates and by your thinking "everything is stalled until more food is added" then that just proves what I have been trying to say. When you add food to get things moving again, your adding food back into the system in the redfield ratio, or worse, slightly skewed towards more phosphates than the redfield ratio, then eventually those phosphates will continue to climb because every time the system "stalls" due to low nitrates, the phosphates will no longer lower. Basic math.. if your adding 2 phosphates a day and 1 nitrate, and you system consumes 1 phosphate and 1 nitrate a day, you will have a left over 1 phosphate when your done.. repeat this day after day and you can see how phosphates can become a problem over time.

  2. #12
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    My scrubber keeps my nitrates at 0.. my Po4 was 2.5 with hanna checker. Scrubber since day one.
    Since i ran gfo over the wekend now both Po4 and No3 are reading 0.. And .03. Either my rock is releasing a ton os phosphates, which is unlikely since they are still 0.03 a week later, or the scrubber removes more nitrates than phosphates.

  3. #13
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    I don't agree that you can't remove more N than P or more P than N, that is easily proven to be false
    Then you must deal in imaginary numbers. Far as a know, removing something which does not exist is not possible. If over the period of one year, you feed one pound of N and one pound of P, you cannot over that same time period remove two pounds of N.

    Anyone can put a ton of GFO in a system that has high nitrates and phosphates and skew the parameters that way.
    You are not skewing anything. The GFO will only remove what P has been put in. No more.

    if all things are equal, algae and bacteria, most systems will likely skew towards a phosphate problem over time because even in barebottom systems there are anaerobic areas within live rock for denitrification bacteria to colonize.
    You are reaching here. Especially with no numbers. That's why I keep is simple, so I don't have to dig up more numbers.

    The sheer volume of "air" on the outside vs inside will quickly equalize the air inside when the door is opened... but I don't see how that relates to phosphates/nitrates and adding food to a system.
    That's exactly how. Putting food in, is opening the window; it resets everything to the original ratios.


    If I have a system with .1 phosphates and 0 nitrates and by your thinking "everything is stalled until more food is added" then that just proves what I have been trying to say.
    No it's the opposite. The system will not continue to "skew"; it will stay where it's at until it's "reset" with more food.

    if your adding 2 phosphates a day and 1 nitrate, and you system consumes 1 phosphate and 1 nitrate a day
    But you are not removing 1 and 1. You are removing 2 and 1... the same that is fed in, whatever that is.

  4. #14
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    Going to side with Randy Holmes-Farley again... I believe in his science and that he is correct.

    Bear in mind that carbon dosing can use a lot more N than P, even by Redfield sorts of ratios, because of nitrate potentially being converted into N2 in low O2 areas like sand beds or in live rock. That process is driven by metabolism of organic matter in low O2 areas, so is potentially greatly enhanced by organic carbon dosing..

    By that means, one can essentially eliminate nitrate will still having substantial P, and that, IMO, is why many folks find it desirable to use other methods at the same time, like GFO or growing macroalgae.

    Alternatively, some folks find it desirable to dose nitrate under the scenario, along for more bacterial growth than the carbon dosing alone promotes, and that allows P to also be consumed.
    Quote Originally Posted by SantaMonica View Post
    But you are not removing 1 and 1. You are removing 2 and 1... the same that is fed in, whatever that is.
    As an example, I add 2 phosphates and 2 nitrate, yet my system consumes 2 nitrate and 1 phosphate (due to anaerobic bacteria doing more work on nitrates), this leads to a skewed system. It does not reset the next time I add food, it only adds to what is already in the tank. If the tank has 0 nitrates and .1 phosphates, and I dump in more food, I do not magically erase the .1 phosphates already in the system, I add to it.

    I am not talking about how an ATS works here, I am speaking about a tank as a whole, which includes bacteria. The ATS will remove stuff at the redfield ratio... bacteria will not always do the same.

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    Can it be that mentioned P puzzle has something to do with coral browning too ? After last discussion that DOC is most likely problem of that I have run GFO and purigen, but this have not changed browning at all. I also have feeling that with time I have more and more to deal with raised P which was not the case when tank was new. Lets say up to 1year mark.

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    Phosphates are a leading cause of coral browning... but also makes corals grow faster. Personally, I think around .03-.07 is good for phosphates, below .03 and you get much slower growth of corals, above .07 and brown corals start to become a concern, although every coral reacts differently. Some can be fine up to .5 phosphates while others will brown out completely at .1. Problem with the browning is the coral just becomes "too healthy" so to speak and over colonizes with zooxanthallae, which gives the coral the brown color. Reducing P will starve some of the zooxanthallae which will make the brown fade away. DOCs are another issue for browning because it is also a food source for the coral, making living on the coral much more enticing to the algae. Lighting is also another cause.. too much light can make happy living conditions for zooxanthallae, but add just a little more light on top of that and it could tip the scale and lead to coral bleaching, where all the zooxanthallae leaves the coral because it is no longer a "happy living place".

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    It’s been quite an interesting topic to follow with many different points of view, but I have to say, and with great respect to SM, that I still think that P will rise over time. I just can’t agree with SM’s analogy. Algae just use more N than P, and once that ratio is greater in P, no amount of “door opening” is going to re-set it( maybe a 100% water change). Of cause I have no idea how the ocean is at the levels it is, and what mechanisms are in place to achieve this, but I would assume by the excessive amount of nuisance algae that you see around inshore waterways , something is out of whack.
    Last edited by leebee; 03-10-2012 at 06:07 PM.

  8. #18
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    Ive heard phosphate levels of 2.5 or higher can inhibit coral growth, first time i hear the absence of phosphate can cause it as well. Any more info on this?

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    Quote Originally Posted by RkyRickstr View Post
    Ive heard phosphate levels of 2.5 or higher can inhibit coral growth, first time i hear the absence of phosphate can cause it as well. Any more info on this?
    Natural reef water would be about 1000 times less that that, I panic when P gets over .03( and I still have cyano !).

  10. #20
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    Quote Originally Posted by RkyRickstr View Post
    Ive heard phosphate levels of 2.5 or higher can inhibit coral growth, first time i hear the absence of phosphate can cause it as well. Any more info on this?
    This article shows that higher phosphates = faster growth for one specific coral tested (although at a point the growth becomes harmful due to growing a less dense skeleton making the corals much more fragile).
    http://www.advancedaquarist.com/blog...opora-muricata

    Wetweb Media has this quote below. Corals require phosphates and nitrates to grow, so a very small amount showing up on a test kit is a good thing. If you have 0/0 readings and are not feeding heavily chances are your probably starving the tank. If you have 0/0 readings in a 100G tank but dump in 10 pre-rinsed cubes of food a day, chances are your system is working perfect but probably wouldn't hurt to add another cube of food so your not bottoming out the available elements in the water column. To me, reef tanks are all about finding a "balance".. it is a bit like a Yo-Yo at first until you get a feel for the tank (and every tank is different and requires getting a feel for it, even if you setup 2 identical tanks side by side, just the different rock will make each tank behave differently), but eventually one should be able to find a natural balance and once you find that, most tanks start to run almost on cruise control at that point (which to many is a distant dream, but it is possible).

    http://www.wetwebmedia.com/ca/volume...phosphates.htm
    The water of natural coral reefs contains very little phosphate, typically around 0.005 ppm, significantly lower levels can result in a kind of coral bleaching (Tissue cannot regenerate anymore), so this should be smallest desirable concentration.
    Serious decrease of coral growth was detected at concentrations above 0.1 ppm. This can be considered ideally as the maximum level you should have in your reef tank with stony corals. 0.25 should do if you only have easy coral species, below 0.1 ppm seems mandatory for the more sensitive ones.
    One more interesting part of that article that I try and inform people about, but I always seem to get laughed at because according to many it has a "minimal effect" but I disagree... which is pre-rinsing frozen food to remove phosphates.
    All foods used for fish and invertebrates contain phosphate (roughly 0.2-3% of its dry weight), but since you have to feed your animals, this input cannot be decreased at first glance. What you can do is keep the thawing water (that is not eaten anyway) out of the aquarium. Why all that rinsing work?

    The thawing water of various frozen foods has been analysed with regard to its phosphate concentration (e.g. by Schwirtz). Contents between 0.74 mg/l (fish eggs thawed for 20 minutes) and 15.53 mg/l (mussel flesh thawed for 2 hours) were measured in 100 ml of RO water, in which about 3 grams of frozen food were thawed. Accordingly, in a 100 gallon tank fed with one un-rinsed 3 gram cube of mussel flesh the phosphate concentration is being raised by 0.0039 mg/l per feeding only by the thawing water. In 100 days without considering large water changes, this would correspond to a phosphate concentration of 0.39 mg/l, a concentration not healthy for corals, and the phosphates introduced by the actual mussel flesh are not even considered in this example. So, rinse your frozen foods!

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