How do you count Nitrogen level (for fish vs plants)? - The Planted Tank Forum
 
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post #1 of 15 (permalink) Old 06-22-2016, 09:14 PM Thread Starter
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Arrow How do you count Nitrogen level (for fish vs plants)?

First, I'm happy to be making my first post here. I've found this site to be an incredible resource over the last year, and I appreciate the contributions of the entire community. Now that I have some questions that I find no existing threads for, I decided it's time I post one myself.

1 year ago, my wife and I started a 46gal freshwater tank. Months later things were very stable. We use an API master test kit and NO3 levels were consistently around 10ppm with our regular water change routine.

Around 6 months ago we started adding plants, and now the tank is very well planted. Since then of course we saw the N03 levels drop to around 2.5ppm. Around 3 months ago we started dosing with Seachem Flourish Nitrogen. Since then our NO3 levels have been 10ppm before each 50% PWC, and logically about 5ppm afterwards.

I would like to maximize the Nitrogen in the tank for our plants' sake, but not harm the fish. We have some particularly sensitive fish, like Otocinclus, so I'd like to keep NO3 at 20ppm or below. So I'm very cautious to raise the amount I'm dosing the tank, lest I hurt the fish...

My question is how do I count Nitrogen? I know the Seachem Nitrogen adds different forms, but the only one I can test for is NO3. I've seen in different places that people suggest multiplying the result of the API NO3 test by 2 to get your total Nitrogen available for plants. Does that make sense? I suppose I could just pay attention to the API results (as NO3 is the only form that could harm the fish) and know that the amount of N available to the plants is always higher than that. Anybody have other suggestions or wisdom about this?

Thanks in advance!
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post #2 of 15 (permalink) Old 06-23-2016, 04:26 AM
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I'm just a small Billy Goat Gruff around here but the bigger Billy Goats aren't answering so I'll take a stab at this. I've never had luck with Otocinclus so I think your 20 ppm is very sensible. I don't know what is meant by Nitrogen. I understand Ammonia, Nitrite and Nitrate and I guess collectively they're all forms of Nitrogen. I have a big jar of Ammonium Chloride I use to cycle tanks with but I wouldn't dose a plant tank with fish in it with it. But I'm reading the label here as I post this and Flourish Nitrogen looks like a great product and I'm sure it's formulated to be safe.

The counting Nitrogen question I don't have an answer for. But the (for fish vs plants) part of the title of your post is very interesting and I think salient for all of us. You say your Nitrate was 2.5 mg/l NO3 before a PWC before you started dosing Nitrogen but you did not say how much Nitrogen you started to dose. According to Seachem's formula on the label, it would take about six caps to get you up around 20 mg/l NO3 after a water change now.

The Flourish Nitrogen label does say you can get a reasonable estimate of the Nitrate level by doubling a Nitrate reading.

Last edited by Savetheplants; 06-23-2016 at 04:44 AM. Reason: miscalculated dose
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post #3 of 15 (permalink) Old 06-23-2016, 04:47 AM
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Would think your nitrate level's as reported are fine, and might not add more nitrogen to encourage more growth? without also adding a bit more of all other nutrient's lest you create a deficiency of another nutrient (ie) liebigs law.(if you buy into it)
The nitrate test kit reading's can be sketchy without calibrating them against known solution and there should be a thread around here somewhere bout it.
If one is not also trying to drive more growth with more light,,then more nitrogen may not be needed, plant's grow slower in lower light,need less nutrient's due to slower metabolisim's.(less light energy driving demand)
I'm all over the place dosing fertz in my low tech tanks cause I like to think I can tell what the plant's are calling for but really..I just add a little bit of all nutrient's once a week or two and maybe a little extra at times of this or that.
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post #4 of 15 (permalink) Old 06-23-2016, 11:44 AM
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Not all of the nitrogen supplied by Flourish Nitrogen is in the form of nitrate so when you're using their fert and measuring nitrate you're not measuring the total amount of nitrogen. Here's a quote from Seachem's site on how to determine your N level, "Because one-half of the nitrogen in Flourish Nitrogen™ is from nitrate you can get a reasonable estimate of nitrogen levels by doubling a nitrate reading."

If you're using Aquavitro Synthesis, another Seachem N supplement, you would have to base your determination on this quote, " This dose increases total nitrogen by 0.24 mg/L. This is the same amount of nitrogen that would be present if all nitrogen were present in the nitrate form at 1 mg/L."

It's going to be the same with any fert that supplies N in any form other than NO3. You'll need to know what percent is supplied by NO3 and from other sources ( urea, ammonium ).
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post #5 of 15 (permalink) Old 06-23-2016, 05:28 PM Thread Starter
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Thank you all for your responses!

I should say that I have left out some of the details to avoid making my question unnecessarily complicated. We do have a medium-strength light, we are dosing several other nutrients in addition to the N (P, K, Flourish Comprehensive) as well as Excel. Through trial and error and some basic calculation I think we've been able to keep the dosing in balance. As roadmaster said, "I like to think I can tell what the plants are calling for...". In general we try to keep things low-tech.

The basic outline of our N dosing for the last 3+ months:
- After our water change, NO3 readings have been 5ppm.
- We are dosing 5ml of Seachem Nitrogen 2x a week:
---- per Seachem - Flourish Nitrogen I calculate with 40gal of water in our 46 gal tank, that each 5ml dose would raise N at the equivalent amount that 2ppm(mg/L) of NO3 would.
- After 2 weeks (4 doses), before our 50% PWC, we would have added 8ppm NO3 equivalent.
- Before our PWC we measure 10ppm NO3, leaving me to assume that the plants have used approximately 3ppm (5 + 8 = 13... but 10 measured).


So the real question comes down to "How can I maximize the N available to plants while also minimizing the NO3 levels for the fish?"

Because I can only measure the NO3 levels (and perhaps not so accurately) I guess the best I can do is dose the Seachem Nitrogen and aim for a target level of NO3. I think it's safe to assume the amount of total N available to plants will be greater than the NO3 level (perhaps it's 2x) but as long as NO3 is at a safe level for fish, the actual level of total N is not so important... right?

If our NO3 is measured at 5ppm after a water change, and increases over 2 weeks to 10ppm, is that optimal for plants or should I aim for a higher target? I actually doubled my Seachem N dose this week, and I'll know in 2 weeks what the NO3 level comes out to at the end of our water change cycle.

Will the plants do any better with NO3 readings of 10-20 as opposed to the current readings of 5-10, or is this just overkill?

Thanks so much.
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post #6 of 15 (permalink) Old 06-24-2016, 03:35 AM
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5-10 ppm is on the low side. Nothing wrong with 15+ ppm as long as you have the plant mass to consume it.

Look for signs of problems with older leaves like big holes and dying older leaves. If it shows up then bump the N. Try bumping the P and K too while you are at it. Usually P is more of an issue as it is typically 0.5 or less unless you are using separate fertilization with P.

Fish can actually tolerate higher nitrate content unless the fish you house are very sensitive.


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post #7 of 15 (permalink) Old 06-24-2016, 04:12 AM Thread Starter
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Thanks, this is very helpful. We have had issues with some older leaves dying and having larger holes. If that is a possible sign of not enough Nitrogen I think I'm going to stick with the increased N dose and aim for 15-20 NO3 just before our water changes. We did just recently increase K after noticing some pinholes on new and old leaves. Also, I was just noticing some "algae dust" forming on the glass this evening... and thought I should increase the P dose to keep up with the increased N (via that 1:10 rule of thumb).

I certainly appreciate input from anyone else with wisdom and experience on this issue.
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post #8 of 15 (permalink) Old 06-24-2016, 05:04 AM
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Look into the elements that plants can transfer from one place to another, (it is only a few, called mobile and immobile). It is a good strategy for dealing with some problems, i.e. you either have these holes and patches where the plant is taking stuff from to provide to new growth, or your problem lies with a nutrients outside of this group.

Mobile nutrients: Magnesium (Mg), nitrogen (N), phosphorus (P), potassium (K), molybdenum (Mo)

Immobile nutrients: Iron (Fe), calcium (Ca), sulfur (S), boron (B)





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post #9 of 15 (permalink) Old 06-24-2016, 07:01 AM
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Quote:
Originally Posted by jbjonas View Post
Thanks, this is very helpful. We have had issues with some older leaves dying and having larger holes. If that is a possible sign of not enough Nitrogen I think I'm going to stick with the increased N dose and aim for 15-20 NO3 just before our water changes. We did just recently increase K after noticing some pinholes on new and old leaves. Also, I was just noticing some "algae dust" forming on the glass this evening... and thought I should increase the P dose to keep up with the increased N (via that 1:10 rule of thumb).

I certainly appreciate input from anyone else with wisdom and experience on this issue.
Increasing N,P and K should stop the older leaves from having issues. The damaged leaves cannot be repaired so you should cut those off and pay attention to the new growth.

The only thing you need to watch is N. P and K can be a bit higher. I've seen people with PO4 as high 5 ppm (I run around 3 ppm) and I used to run my tank with as high as 60+ K with no issues.

I helped my neighbor setup a low light non-CO2 planted tank. She ran her tank for 40+ ppm NO3 for more thank a month and the plants loved it. Too bad she had no CO2 because I could see the plant struggling a bit with size.


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post #10 of 15 (permalink) Old 06-24-2016, 04:54 PM Thread Starter
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Thank you so much.

Quote:
Originally Posted by PortalMasteryRy View Post
The only thing you need to watch is N. P and K can be a bit higher. I've seen people with PO4 as high 5 ppm (I run around 3 ppm) and I used to run my tank with as high as 60+ K with no issues.
I was aware that K can really be very high without any issues, so we're dosing that generously.

From what I've read, P (particularly PO4) can be an issue if too high or too low - in that it can promote algae growth. So we have been very careful there and attempting to meet the recommended ratio of 10 NO3 : 1 PO4.

As far as N levels, that was my intent in starting this thread... It sounds like other than concerns for the fish, N can be as high as possible. I'm going to aim for NO3 levels between 10-20, as opposed to our current 5-10. That sounds like a good bet.

Quote:
Originally Posted by PortalMasteryRy
5-10 ppm is on the low side. Nothing wrong with 15+ ppm as long as you have the plant mass to consume it.
Are there any other opinions on this point? I have read other opinions that having more than 10ppm available to your plants won't make any additional difference.
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post #11 of 15 (permalink) Old 06-24-2016, 05:30 PM
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Originally Posted by Nordic View Post

I haven't seen this one yet, thanks for sharing. Since it specifies the corn plant, to what extent should we generalize the symptoms to aquatic/submersed?
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post #12 of 15 (permalink) Old 06-24-2016, 05:59 PM
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Don't see any reason it should be different, apart from aquatic plants not drying out. I think if you read the descriptions they add to each other.

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post #13 of 15 (permalink) Old 06-25-2016, 01:52 AM
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Originally Posted by jbjonas View Post
Thank you so much.



I was aware that K can really be very high without any issues, so we're dosing that generously.

From what I've read, P (particularly PO4) can be an issue if too high or too low - in that it can promote algae growth. So we have been very careful there and attempting to meet the recommended ratio of 10 NO3 : 1 PO4.

As far as N levels, that was my intent in starting this thread... It sounds like other than concerns for the fish, N can be as high as possible. I'm going to aim for NO3 levels between 10-20, as opposed to our current 5-10. That sounds like a good bet.



Are there any other opinions on this point? I have read other opinions that having more than 10ppm available to your plants won't make any additional difference.
10 ppm on a high light CO2 injected tank is not going to cut it. I know because at 10 ppm some of plant's older leaves (very bottom) are showing holes and are dying out. 10-20 ppm Nitrate is actually still very safe for fish and I've ran my 40B with 30 ppm Nitrate for 6 months without any issues with fish and I've got a breeding colony of platys. If you have discuss then it might be an issue. I have otos too if you are concerned about them. I still have 7 of the original 8 otos that I bought when I first started my tank. I have 2 female otos that always show eggs in their belly.

It really depends on the setup but the reason we go for higher (not toxic) level of nutrients is to simply rule out any issues with the nutrient levels leaving usually CO2 as the only limiting component.


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post #14 of 15 (permalink) Old 06-25-2016, 02:57 AM Thread Starter
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Quote:
Originally Posted by PortalMasteryRy View Post
10 ppm on a high light CO2 injected tank is not going to cut it. I know because at 10 ppm some of plant's older leaves (very bottom) are showing holes and are dying out. 10-20 ppm Nitrate is actually still very safe for fish and I've ran my 40B with 30 ppm Nitrate for 6 months without any issues with fish and I've got a breeding colony of platys. If you have discuss then it might be an issue. I have otos too if you are concerned about them. I still have 7 of the original 8 otos that I bought when I first started my tank. I have 2 female otos that always show eggs in their belly.

It really depends on the setup but the reason we go for higher (not toxic) level of nutrients is to simply rule out any issues with the nutrient levels leaving usually CO2 as the only limiting component.
I would call what we have medium light, and we are not using CO2 (just Excel). Definitely keeping it low-tech. But either way, it sounds like the more Nitrogen the better.

I guess even if our plants can't use more N than is available at 10ppm NO3, it still can't hurt to give them more than they need right? It seems that the predominant advice is still to aim for 10-20. Thanks!
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post #15 of 15 (permalink) Old 07-19-2016, 04:53 PM Thread Starter
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So things have been going well overall. After upping our N dose to 10 ml twice a week I saw the API test results go up to about 20-25ppm at their peak during our water change cycle. Unfortunately we did have an Oto die that first time through the cycle (whether it was related or not I can't say, although he was large and had been in the tank for maybe 6 months or more). After that we reduced our dose to 7.5 ml and we're aiming to keep the peak N level at 20ppm or below. As far as the plants, our rotella garden has grown like mad with the additional Nitrogen availability. Still watching the leafy plants, which seem to grow much more slowly in general, so it might be a few months before we can tell if they are really benefiting from the additional N in the tank. Thanks again everyone.
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