NO3:PO4 Generation And Consumption - The Planted Tank Forum
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post #1 of 16 (permalink) Old 10-12-2017, 07:36 PM Thread Starter
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NO3:PO4 Generation And Consumption

This is not a problem, but more of an exercise. I’ve been wondering about nitrate and phosphate generation by fauna and consumption by plants.

Although I suspect that there may be consistent generation and consumption ratios of N and P, regardless of setup, my particular setup is high tech, EI dosing (except for NO3), 50% weekly RO/DI wc and KH/GH both kept in the 4-5 degree area. I have very healthy plants.

My curiosity is around the odd, to me, need to add PO4 throughout the week. My fauna load is heavy by normal standards, so my NO3 levels are always in the 20-30 ppm level throughout the week (I add no N products), but PO4 always drops (within a day after I add it) to the 2.0 area, then drops further toward the end of the week. While this roughly reflects the nominally ideal 10:1 ratio (which I don’t try to maintain), it also seems to indicate that PO4 is consumed more rapidly by plants than NO3 (I thought the opposite was the case) OR …NO3 is generated at a much greater than 10:1 ratio by fauna. Maybe both?

I realize that the type of food administered and type of plants may affect these ratios, as well as other possible aspects (light, CO2, etc.) but would these variables cause dramatic variations in the NO3: PO4 generation and consumption ratios?

Do we know if there is a roughly fixed ratio of NO3: PO4 generated by fauna?

Do we know if there is a roughly fixed ratio of NO3: PO4 consumed by plants?
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Last edited by Deanna; 10-12-2017 at 07:38 PM. Reason: add
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post #2 of 16 (permalink) Old 10-13-2017, 12:00 AM
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Great topic, following to learn


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post #3 of 16 (permalink) Old 10-18-2017, 10:30 PM Thread Starter
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Great topic, following to learn
Looks like no one reading this feels competent enough to address it. I'll try to keep it active every week or so to see if such an expert cruising TPT notices it.
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post #4 of 16 (permalink) Old 10-20-2017, 02:57 AM
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post #5 of 16 (permalink) Old 10-20-2017, 04:25 AM
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NO3:PO4 Generation And Consumption

Well. Not an expert, but adding to the brainstorming. I recall in terrestrial gardening, different npk combo fertilizers are added to achieve different objectives. A quick google found this link http://www.sunset.com/garden/garden-...se-fertilizers that reminded me of which ones were for what. However, it also mentioned that the growing season should be considered in what to add. I never even considered that originally! Living in FL with mostly one season, I tend to forget about that. So thanks for starting this thread to improve my other garden. Anyway, I digress. What if our tank plants are doing their thing based on their growing season or needs? So say you did a bottom trim and it needs to regrow its roots, itís probably going to suck up more P to do so? And on the other point, how does it know what season it is? I mean my tank never wavers from the 70s too much and I sure never change the photoperiod to match the seasons. I wonder if I should. I wonder if our plants would be healthier if it got seasons. Sort of like humans needing their circadian rhythms. Maybe theyíve adapted. Oh, what mutated specimens have we wrought?! Sorry. I think Iíve rambled enough now. @Deanna, I know you have a much more scientific thought process than I do so please forgive my irreverence. I will stay quiet and just follow now as I really am interested in what findings come out of this.


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post #6 of 16 (permalink) Old 10-20-2017, 05:02 AM
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Stop worrying about ratios of nutrient's is my philosophy.
I just try to see that plant's have all nutrient's in excess of particular plant mass,feeding schedule for fishes,types of plant's,light energy driving growth,CO2 or non CO2.
At the end of the week,I perform large water change and Re-dose 1/4 EI values for low tech.
If it were high tech,I would dose full EI values.
Would not try and get wrapped around the wheel regarding ratios when so many variables are at play.
By adding nutrient's in excess of what plant's might need,you can eliminate to a large degree nutrient deficiency.
Leaves only light and CO2 as possible limiting factor from plant perspective.
Do not believe one can find ideal ratio when plant mass is increasing daily/weekly.
What might have been just right last week ,may not be enough three week's from now.
Might be good topic for discussion but too many variables to consider to find any real values.
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post #7 of 16 (permalink) Old 10-20-2017, 06:55 AM
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Interesting and complicated subject.

Quote:
Originally Posted by Deanna View Post

would these variables cause dramatic variations in the NO3: PO4 generation and consumption ratios?
Yes

Quote:
Originally Posted by Deanna View Post
Do we know if there is a roughly fixed ratio of NO3: PO4 generated by fauna?
]

There is none. It depends on the feed and needs of each organism. Different types of fish have dif dietary requirements and will therefore excrete different amounts of things. You may be able to find a mean value but why would a mean value apply to your aquarium?

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Do we know if there is a roughly fixed ratio of NO3: PO4 consumed by plants?
Again on average yes, however in one aquarium the amounts and ratios will differ from one day to the next. Plants are able to make nutrient reserves, this means there will be high uptake at first, and then possibly even higher of some nutrients, without a good ROI.

Also do not ignore the bacterial population of your aquarium. They are major contributors in generating No3 and are also able to consume good amounts of PO4 and Fe. If conditions are right you will need an ever increasing amount of Po4 to feed the bacteria and leave something for the plants. This happens until bacteria run into a limiting factor, oxygen, space other nutrient. What does this do to the nutrient ratios?

I agree, don't worry about ratios. Dose to have enough.

Rant:
Speaking in general when describing a ratio it is good practice (although largely ignored) to give units or at least what was measured, ie

10:1 N:P by volume is not the same as
10:1 N:P g:mg or
10:1 N:P by weight or
10:1 N:P mol

Believe it or not I can even say 10:1 N:P by grains of my particular salt and use the ratio adequately. A percentage % or ppm or ppt are also ratios, whereas mg/L is is not and gives you all the information needed.

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post #8 of 16 (permalink) Old 10-20-2017, 11:05 AM
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Well,it's a bit like tryin to nail jelly to the wall.
Fish food's produce nutrient's like phosphates,(just one for example) and one might be able to gauge how much by % of content or feedings, but can only estimate what % of the food is actually retained by a fish or group of fishes.
Seldom hear about temperatures driving fishes and plant's metabolisim's but temp too is another variable among a bunch of em.
Tank maint ,plant maint,etc.etc.
Me thinks we can find the balance for our own particular tank, but maybe not any number that might work for the majority.
Keeping light proton's/energy in check /proper ratios,, might be a more interesting experiment even with good CO2 management and nutrient availability.
Most I imagine,could find interesting result's.
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post #9 of 16 (permalink) Old 10-20-2017, 03:44 PM Thread Starter
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Thanks, to all, for the input. The general consensus seems to be that expecting a fixed ratio, primarily for plant uptake is, in fact, too dependent upon many variables and is not common to all aquatic plants. Additinoally, such ratios for supply of NO3 and PO4 are even more dependent upon many variables, not least of which is the BB - which I hadn't considered.

I agree about ignoring ratios in terms of trying to maintain them. It just seemed odd that my PO4 drops through the week while my NO3 holds steady or climbs somewhat, creating a constantly changing ratio of the two. Thus, the initial question.
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post #10 of 16 (permalink) Old 10-20-2017, 04:12 PM
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Well the BB (beneficial bacteria) are almost wholly reliant on organic input from me/you along with fish food's,fish waste, and or decaying plant matter, and most importantly...Oxygen.
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post #11 of 16 (permalink) Old 10-20-2017, 07:57 PM
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Quote:
Originally Posted by ipkiss View Post
Well. Not an expert, but adding to the brainstorming. I recall in terrestrial gardening, different npk combo fertilizers are added to achieve different objectives. A quick google found this link Fertilizer Crash Course - Sunset that reminded me of which ones were for what. However, it also mentioned that the growing season should be considered in what to add. I never even considered that originally! Living in FL with mostly one season, I tend to forget about that. So thanks for starting this thread to improve my other garden. Anyway, I digress. What if our tank plants are doing their thing based on their growing season or needs? So say you did a bottom trim and it needs to regrow its roots, itís probably going to suck up more P to do so? And on the other point, how does it know what season it is? I mean my tank never wavers from the 70s too much and I sure never change the photoperiod to match the seasons. I wonder if I should. I wonder if our plants would be healthier if it got seasons. Sort of like humans needing their circadian rhythms. Maybe theyíve adapted. Oh, what mutated specimens have we wrought?! Sorry. I think Iíve rambled enough now. @Deanna, I know you have a much more scientific thought process than I do so please forgive my irreverence. I will stay quiet and just follow now as I really am interested in what findings come out of this.
The majority of the plants in the hobby are tropical. Many tropical places don't have seasons so they aren't "seasonal plants".
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post #12 of 16 (permalink) Old 10-20-2017, 08:20 PM
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There are also some CBBB, can't be bothered bacteria, which will grow in numbers whenever we provide enough nutrients for them. A very visible example is the white biofilm that forms on the top of the water when a lot of iron is dosed. They reduce the iron levels but do nothing good or bad in some way. Other bacteria will bloom when other nutrients are increased.

I know where you are @Deanna . I was at one point dosing 2-3mg/L PO4 and seeing 1mg/L PO4 the next day. I tested the water for iron frequently and there was no large drop there. I then stepped back and reduced my PO4 to EI levels and nothing bad happened. Sometimes we need to take the foot of the gas pedal and enjoy the autumn colors... and plan our next aquascape

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The majority of the plants in the hobby are tropical. Many tropical places don't have seasons so they aren't "seasonal plants".
Yes, that also jumped in my eyes a little but to be fair, some plants come from a dry / wet season area. They will usually be emersed and flower in the dry season. It would be interesting to see if some plants do better if they are allowed to go through this cycle.

One are the post also addresses is that of "plant seasons" as in adaptation,rooting, growing, flowering. The different requirement for nutrients was shown in Arabidopsis (model terrestrial plant) but I have zet to show any suggestive research with aquarium plants.

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post #13 of 16 (permalink) Old 10-21-2017, 12:59 AM Thread Starter
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I know where you are @Deanna . I was at one point dosing 2-3mg/L PO4 and seeing 1mg/L PO4 the next day. I tested the water for iron frequently and there was no large drop there. I then stepped back and reduced my PO4 to EI levels and nothing bad happened. Sometimes we need to take the foot of the gas pedal and enjoy the autumn colors... and plan our next aquascape
Yes: odd. However, in my case, I'm going to keep the PO4 in the 3-5 ppm area to help dampen GSA.
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post #14 of 16 (permalink) Old 10-24-2017, 10:06 AM
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Stop worrying about ratios of nutrient's is my philosophy.
So why arenít you adding 10 mg/l of every nutrient weekly ?
Try to grow plants with Ca=5 Mg=40 PO4=10 and NO3=1 . I have read that there are some persons with no issue and CO2 is resolving all problems
Every of those nutrients are at "+" so should be no problem. But for sure will be.
Ratios with some +/- margins are most important things in this hobby. Specially if you don have a buffer in case of active soil.
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post #15 of 16 (permalink) Old 10-24-2017, 10:36 AM
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So why aren’t you adding 10 mg/l of every nutrient weekly ?
Try to grow plants with Ca=5 Mg=40 PO4=10 and NO3=1 . I have read that there are some persons with no issue and CO2 is resolving all problems
Every of those nutrients are at "+" so should be no problem. But for sure will be.
Ratios with some +/- margins are most important things in this hobby. Specially if you don have a buffer in case of active soil.

I use modified version of Estimative Index (dosing for dummies). in my low tech tanks.
Happily leave others to ponder /experiment with proper ratio's.
We all experiment don't we ???
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