# High Nitrates....Bad for Plants?



## smiller

I know that sometimes there is a big understanding about fish and high nitrates. I see it here and on other boards all the time. Most fish can in reality take a pretty high nitrate level without stress as long as everything else is in line. What I am curious about is if plants actually like a higher level than the range we shoot for or if a level of say 50 or more long term is bad for them?


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## micheljq

smiller said:


> I know that sometimes there is a big understanding about fish and high nitrates. I see it here and on other boards all the time. Most fish can in reality take a pretty high nitrate level without stress as long as everything else is in line. What I am curious about is if plants actually like a higher level than the range we shoot for or if a level of say 50 or more long term is bad for them?


Hi,
Not really a problem for plants, a lot of fishes do not like high nitrates too, many are quite sensible to nitrates. 

Michel.


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## happi

honest answer is, that it does matter, it also depend on the plant species. most plants dont mind about the high nitrate and some will get stunted and stop growing or not grow at all. i carried a test and i can confirm this while most here will disagree with me. some plants doesnt grow at in nitrat dosing only, they grew better for me in Ammonium dosing (fish also produce this). if you have many fishes and many plants you can carry this test youself, you will notice nitrate going up while your plants growing well at the same time, they are using ammonium from fish waste before it gets converted to nitrate, that mean they are using less nitrate compare to ammonium. 

i hope this help


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## BBradbury

*Aquarium Plant and Nitrates*



smiller said:


> I know that sometimes there is a big understanding about fish and high nitrates. I see it here and on other boards all the time. Most fish can in reality take a pretty high nitrate level without stress as long as everything else is in line. What I am curious about is if plants actually like a higher level than the range we shoot for or if a level of say 50 or more long term is bad for them?


Hello sm...

Plants prefer nitrogen rich water. That's why it's good to have a lot of plants in a tank during the cycling process. They help use ammonia (NO) and nitrite (NO2) and nitrates (NO3). Fish are the opposite. High levels of nitrogen is toxic to them. Specifically damaging sensative gill tissues. 

Ideally, you want to keep ammonia and nitrite at "0" and nitrates in the 20 to 30 ppm range. Higher nitrates over an extended period aren't good for your fish.

B


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## smiller

BBradbury said:


> Hello sm...
> 
> Plants prefer nitrogen rich water. That's why it's good to have a lot of plants in a tank during the cycling process. They help use ammonia (NO) and nitrite (NO2) and nitrates (NO3). Fish are the opposite. High levels of nitrogen is toxic to them. Specifically damaging sensative gill tissues.
> 
> Ideally, you want to keep ammonia and nitrite at "0" and nitrates in the 20 to 30 ppm range. Higher nitrates over an extended period aren't good for your fish.
> 
> B


My 150 has been running now since last April so my tank has been cycled for a long time. I started low tech with a medium plant load. I recently increased lighting and added CO2 and now am heavily planted, dosing EI. Most everything looks pretty good except my nitrate always seems to run a little high. I calibrated my test kit but still don't trust it. I have a different brand kit on order. I'm guessing after my first potassium nitrate dose of the week nitrate to be in the 40 range if the test kit is correct with calibration adjustment. I don't have anything that IMO would cause an unusually high nitrate reading. I do have a decent fish load but not by any means an overly heavy load. I feed lightly and I vacuum the substrate weekly if needed. Usually there is very little waste to vacuum. Basically to me it comes down to either an unreliable test kit reading even after calibration or the plants are not taking in much nitrate. Being semi new to planted tanks I don't know what the chances of the later are.


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## BBradbury

*High Nitrates*

Hello again sm...

Large, frequent water changes will help. If you use dry ferts, then you're surely doing this already. The other thing that came to me was, a company by the name ACUREL has a nitrate reducing medium, that may help. I've used their poly fiber media for a while and like it. They've been in business for a long time and have some very good aquarium products.

B


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## smiller

BBradbury said:


> Hello again sm...
> 
> Large, frequent water changes will help. If you use dry ferts, then you're surely doing this already. The other thing that came to me was, a company by the name ACUREL has a nitrate removing medium, that may help. I've used their poly fiber media for a while and like it. They've been in business for a long time and have some very good aquarium products.
> 
> B


Yes, I do a weekly 50-60% water change. 

I don't really want to use a product which pulls out nitrate unless it gets totally out of control. I don't think I am by any means at that point yet, even if my level really is 50. 

Thanks for all of your advice.


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## musician71604

I may be totally off base here, but have you checked your filter to see if it has accumulated a bunch of debris?


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## smiller

musician71604 said:


> I may be totally off base here, but have you checked your filter to see if it has accumulated a bunch of debris?


I broke down my FX5 about 3 weeks ago and washed all of the media and cleaned it well. I had not done that in several months. I can't imagine that would be the issue but it's definitely worth looking at just to be sure. I'll be away for a few days but will do that next week.


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## happi

you have ignored the fact i have written.

have you try cutting down the KNO3 dosing to see what happen?? 

what are your water parameter?


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## DarkCobra

Define "high nitrates". Everyone will do it differently.

At 70-140ppm nitrate (weekly range), I saw stunting and slow growth in many varieties of plants. Signs of phosphate deficiency, despite levels of 30ppm. Uncontrollable algae. The fish, oddly enough, were fine.

This due to a heavy fish load combined with EI dosing. I didn't trust my test kit either, so I bought another much more expensive one. Same result. Weighted my fish food with a gram scale, converted the nitrate/phosphate content to an equivalent amount of dry ferts based on the manufacturer's elemental breakdown, ran everything through Wet's calculator. Again, same result.

I stopped dosing the nitrate/phosphate parts of EI and now everything's peachy.

If asked for exact numbers, I say 20ppm is a good target, 60ppm nitrate is the max one should allow. Will some plants grow better at 60ppm than 20ppm? Or some worse? You'd have to experiment with each individual plant variety. But 20ppm will grow any plant adequately.

Some people even have better plant growth if they keep nitrates well below 20ppm, and other macros similarly reduced. These people typically have soft water, and there's some speculation of a connection.

Experiment and see what works best for you, in your own tank.


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## smiller

happi said:


> you have ignored the fact i have written.
> 
> have you try cutting down the KNO3 dosing to see what happen??
> 
> what are your water parameter?


I haven't ignored you at all. I did not dose KNO3 today. I do not plan to stop dosing KNO3 but I do plan to cut back slowly on it and see how the plants react. From what I am reading that is how it is normally done, and I do know that some end up not dosing KNO3, but I don't think that is the norm. If I end up there then all the better. 

ammonia- 0
nitrite-0
nitrate-30 to 50. less than 20 after weekly water change. (this based on believing my API kit/calibrated)
phosphate 3-5
pH 6.75
KH 12+ (very hard water area)
temp 79


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## smiller

DarkCobra said:


> Define "high nitrates". Everyone will do it differently.


Exactly, as with many things. I've kept mostly SW for the last 30 years so I still have a whole lot to learn about planted tanks, but some things are consistent. What works for some people can be a total disaster for others. 

I've read quotes from "experts" over the years of keeping certain fish long term in 200ppm with no issues. I've read posts from people who kept plants long term in 80ppm and posts from people who blamed plant and fish death on 20ppm.


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## smiller

DarkCobra said:


> At 70-140ppm nitrate (weekly range), I saw stunting and slow growth in many varieties of plants. Signs of phosphate deficiency, despite levels of 30ppm. Uncontrollable algae. The fish, oddly enough, were fine.
> 
> This due to a heavy fish load combined with EI dosing. I didn't trust my test kit either, so I bought another much more expensive one. Same result. Weighted my fish food with a gram scale, converted the nitrate/phosphate content to an equivalent amount of dry ferts based on the manufacturer's elemental breakdown, ran everything through Wet's calculator. Again, same result.
> 
> I stopped dosing the nitrate/phosphate parts of EI and now everything's peachy.
> 
> If asked for exact numbers, I say 20ppm is a good target, 60ppm nitrate is the max one should allow. Will some plants grow better at 60ppm than 20ppm? Or some worse? You'd have to experiment with each individual plant variety. But 20ppm will grow any plant adequately.
> 
> Some people even have better plant growth if they keep nitrates well below 20ppm, and other macros similarly reduced. These people typically have soft water, and there's some speculation of a connection.
> 
> Experiment and see what works best for you, in your own tank.


 I haven't kept (high tech) plants long enough to know how to gauge growth yet. Mine has been pretty good over the last month since changing to CO2/LEDs but don't know if it is where it should be. I was getting a little brown algae growth so I cut back my lighting to one strip from two and it went away pretty quickly so I think I am close to being dialed in.

You and happi really have me thinking about the KNO3 dosing.Thanks very much to both of you.


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## happi

*DarkCobra *is right about people with soft water, this is well tested fact by me and i can confirm this, when i was dosing EI, nitrate levels reach very high and it did not help the plat grow any better in very soft water, however in hard water we can reach high levels of nitrate while having good plant growth. i once documented that some of my plants grew very fast at 70+ppm of nitrate with hard water, plant like blyxa japaonica, they love high nitrate, this is the plant you can try.


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## happi

smiller said:


> I haven't ignored you at all. I did not dose KNO3 today. I do not plan to stop dosing KNO3 but I do plan to cut back slowly on it and see how the plants react. From what I am reading that is how it is normally done, and I do know that some end up not dosing KNO3, but I don't think that is the norm. If I end up there then all the better.
> 
> ammonia- 0
> nitrite-0
> nitrate-30 to 50. less than 20 after weekly water change. (this based on believing my API kit/calibrated)
> phosphate 3-5
> pH 6.75
> KH 12+ (very hard water area)
> temp 79


 
what kind of plants are you keeping? those KH numbers look quite high and the plants you might be trying to keep might not be suitable for that water, this mght be another case your nitrate are high and plants arent using them.


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## plantbrain

I add about 45 ppm a week of NO3, as KNO3 to my 120 and 180.

The tanks are very well fed with lots of fish.

As the tanks also have high light and a lot of stem plant cover, this ends up runnign about 10-20 ppm a week. 
Can I add more without issues? You bet.

Does it help or hinder the plants to do so? No.
I have some so called "fussy" plants. I see little use in adding more NO3 and little improvement beyond this amount for most any light or CO2 level as an upper bound. I think 99.5% of all other planted tanks will use less than this rate.

But...if I do add more, I've never once found any negative issues with plants independent of other factors. I have some client's with automated dosing, they would fiddle with things, then the next day the entire 2 week's worth of ferts would end up in the aquarium. I never got any algae bloom, fish, plants etc were fine.

I see no evidence in research(Gerloff 1966) or within my own experiences and eyeballs that suggest that 40-80 ppm is "bad", but I see no need to go that high on purpose either. 

Another way to test the effect is with hydroponics, since the light and CO2 will easily be non limiting, thus independent. This is different from aquariums, but aquariums can vary greatly for light and CO2, and those 2 things cause DRAMATIC differences in terms of growth, nutrients as long as they do not too limiting have little effect if those two main players are addressed.

Focus there, dose less(assuming your readings are calibrated and correct), check the test kits, watch the plants, fish much more. EI is a starting point, you can easily reduce it down as you see fit till you see a negative plant response (not algae!!!). Algae are not limited by plants ferts no matter how lean you dose. Their needs are 1-3 orders less than common aquarium levels.

For new people, it's hard to know what to look for(I had no clue way back when), but nice pics of healthy plants will give an idea of what to strive for.
It is also good idea to post pics of the set up, the tank etc. People often over look something or have a specific goal in mind. Pics are good for that reason.


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## smiller

Tom,

Thanks for your informative post. That actually wrapped up things I was wondering about very nicely.

My tank did not have a lot of stem plants until the last week. I have just now added enough to fill in all of my empty spaces.....probably in the neighborhood of 50-60 cuttings. We will see if that makes any difference in KNO3 uptake. For now I plan to cut back my dosing and monitor nitrate closely to see where it goes from here. 

Most of my plants are noticeably growing now since I started EI and CO2. Pre-CO2 I had some GSA on anubia leaves, that has ceased. I initially had some brown algae on some of the sand and a little fuzz algae on a few plants leaves, cut back on lighting and that is quickly backing off. I have seen pictures of your tanks and other tanks here so I know the direction I need to go. As far as fish, I am almost 40 years experienced there so that is one area that I do know what to look for. 

The phrase you use, "negative plant response", is that simply a lack of growth or is it more than that?


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## smiller

happi said:


> what kind of plants are you keeping? those KH numbers look quite high and the plants you might be trying to keep might not be suitable for that water, this mght be another case your nitrate are high and plants arent using them.


I don't know what many of my plants are. I always ask questions before I buy such as high light/med light/lower light but I don't keep track of the names. I have a few anubias, swords, crypts, and an assortment of others.


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## happi

smiller said:


> I don't know what many of my plants are. I always ask questions before I buy such as high light/med light/lower light but I don't keep track of the names. I have a few anubias, swords, crypts, and an assortment of others.



all those listed plants are slow grower and mostly root feeders, they will take some benefits from EI dosing but they will mainly feed from roots, having nutrients rich substrate will help with this. you can also try dosing low light EI dosing, which IMO is better choice for your setup.


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## plantbrain

smiller said:


> Tom,
> 
> Thanks for your informative post. That actually wrapped up things I was wondering about very nicely.
> 
> My tank did not have a lot of stem plants until the last week. I have just now added enough to fill in all of my empty spaces.....probably in the neighborhood of 50-60 cuttings. We will see if that makes any difference in KNO3 uptake. For now I plan to cut back my dosing and monitor nitrate closely to see where it goes from here.
> 
> Most of my plants are noticeably growing now since I started EI and CO2. Pre-CO2 I had some GSA on anubia leaves, that has ceased. I initially had some brown algae on some of the sand and a little fuzz algae on a few plants leaves, cut back on lighting and that is quickly backing off. I have seen pictures of your tanks and other tanks here so I know the direction I need to go. As far as fish, I am almost 40 years experienced there so that is one area that I do know what to look for.
> 
> The phrase you use, "negative plant response", is that simply a lack of growth or is it more than that?



Full EI is not needed for moderate or sparse planting.
Doing so should not harm the tank, plants etc, but it's not needed either.

Evidence is lacking IME/IMO that states otherwise, however, there's something called common sense approach. Why add 5X more when 1-2x does the trick? Does little good. But there is little risk and it's a non emergency type of thing certainly.

I find little reason/rational to argue against that even if it poses no demonstrated risk. 

When starting a new plant tank, pack the sucker full of plants, as much as you can stuff in there, after 1-2 months, then thin things out. Water changes, do lots of them in that same time frame, 1-2 months, then back off to once a week etc, maybe less with experience. 

I see plant negative response as many different things, algae is the worse(virtually always something related to CO2), then deformed smaller tip growth(CO2) and then finally a lull in the normal growth rates, this might occur on only one plant species(minor issue), or it might be tank wide.

Like anyone, I neglect tanks every so often and know what needs done if I do. I also try and keep up and response quick is something does happen if I'm being active about keeping up on the tank. 

CO2 tweaking and adjustment is the single HARDEST thing for anyone new with planted tanks will learn about. Reduction of light also can make huge changes and differences. Generally low to moderate light and good rich CO2= best combo for many newbie's goal/s.

A good overview on CO2 and light:

http://www.tropica.com/en/tropica-abc/basic-knowledge/co2-and-light.aspx


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## smiller

plantbrain said:


> Full EI is not needed for moderate or sparse planting.
> Doing so should not harm the tank, plants etc, but it's not needed either.
> 
> Evidence is lacking IME/IMO that states otherwise, however, there's something called common sense approach. Why add 5X more when 1-2x does the trick? Does little good. But there is little risk and it's a non emergency type of thing certainly.
> 
> I find little reason/rational to argue against that even if it poses no demonstrated risk.
> 
> When starting a new plant tank, pack the sucker full of plants, as much as you can stuff in there, after 1-2 months, then thin things out. Water changes, do lots of them in that same time frame, 1-2 months, then back off to once a week etc, maybe less with experience.
> 
> I see plant negative response as many different things, algae is the worse(virtually always something related to CO2), then deformed smaller tip growth(CO2) and then finally a lull in the normal growth rates, this might occur on only one plant species(minor issue), or it might be tank wide.
> 
> Like anyone, I neglect tanks every so often and know what needs done if I do. I also try and keep up and response quick is something does happen if I'm being active about keeping up on the tank.
> 
> CO2 tweaking and adjustment is the single HARDEST thing for anyone new with planted tanks will learn about. Reduction of light also can make huge changes and differences. Generally low to moderate light and good rich CO2= best combo for many newbie's goal/s.
> 
> A good overview on CO2 and light:
> 
> http://www.tropica.com/en/tropica-abc/basic-knowledge/co2-and-light.aspx


I believe I came across this article before, I'm guessing from you linking it on one of your previous posts. Definitely worth another read. 

The tank light preaching I see here can not be overstated. When I fired up the CO2 and EI about a month ago I started at a pH of 8.25 and increased it daily and slowly, watching for plant changes, fish behavior and signs of algae. After two weeks I was at a pH of around 6.70. Drop checker was green, maybe a hair into the yellow end and I was seeing all kinds of new plant growth. I also started seeing some thin brown algae on the substrate, which looked like diatoms but I have no idea if it was in a 9 month old tank with no sign of it before, a few strands of what I call string algae on a couple of plants and also some fuzzy algae on a couple of plants. I turned off one LED strip, which was 40% of the lighting, and it all went away quickly.

Going back to the original question that dealt with nitrates....one more question about EI and scaling that back. You and I talked a week or so back about phosphate levels. My calibrated reading still seems a little low to me, best guess reading the chart in the 3 max range. If EI dosing is cut back due to something like high nitrates how does one keep phosphate levels up? I'm assuming I would cut back or cease with the KNO3 based on my current levels but maybe increase the KHP204? I now dose 3/8 tsp of that 3X week in 160 (including sump) gallons. Would that be unusual to have to increase one and decrease another?


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## Rusticdr

DarkCobra said:


> Define "high nitrates". Everyone will do it differently.
> 
> At 70-140ppm nitrate (weekly range), I saw stunting and slow growth in many varieties of plants. Signs of phosphate deficiency, despite levels of 30ppm. Uncontrollable algae. The fish, oddly enough, were fine.
> 
> This due to a heavy fish load combined with EI dosing. I didn't trust my test kit either, so I bought another much more expensive one. Same result. Weighted my fish food with a gram scale, converted the nitrate/phosphate content to an equivalent amount of dry ferts based on the manufacturer's elemental breakdown, ran everything through Wet's calculator. Again, same result.
> 
> I stopped dosing the nitrate/phosphate parts of EI and now everything's peachy.
> 
> If asked for exact numbers, I say 20ppm is a good target, 60ppm nitrate is the max one should allow. Will some plants grow better at 60ppm than 20ppm? Or some worse? You'd have to experiment with each individual plant variety. But 20ppm will grow any plant adequately.
> 
> Some people even have better plant growth if they keep nitrates well below 20ppm, and other macros similarly reduced. These people typically have soft water, and there's some speculation of a connection.
> 
> Experiment and see what works best for you, in your own tank.


I know this post is abt 4 years old. But definitely worth replying to. I am kinda experiencing the same thing. All my stems reacting badly with no growth at all in a co2 rich high light tank showing 160 ppm nitrate and more than 10 ppm phosphate. Gonna make several water changes and cut down on ei dosing. Thanks. 

Sent from my SM-G920I using Tapatalk


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## Hilde

Now I know why when my nitrates went up to 80 the fish, Serpae Tetra, were not stressed. Unfortunately then I started having string algae.


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## klibs

Rusticdr said:


> I know this post is abt 4 years old. But definitely worth replying to. I am kinda experiencing the same thing. All my stems reacting badly with no growth at all in a co2 rich high light tank showing 160 ppm nitrate and more than 10 ppm phosphate. Gonna make several water changes and cut down on ei dosing. Thanks.
> 
> Sent from my SM-G920I using Tapatalk


there is a lot of good information in this topic. happi and darkcobra bring up a lot of valuable points.

i agree you have way too much of both nutrients. do some water changes and dose a lot less... my tank does the same thing. whenever i see stunting / issues in my tank i immediate test out my macro nutrients. in my tank, when nitrates are high (50+) phosphates are also usually high (4+). when i change some water and cut back a bit on dosing things do much much better. Fish were totally fine the entire time.

personally, my high tech tank gets ideal results when nutrients are kept LOW. nitrates <20, etc... I dose far less than EI levels and my tank is quite densely planted with high light

please reply back with what happens when you cut back on dosing and bring your N/P levels down to reasonable levels.


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## Rusticdr

So glad to hear that u faced a similar situation. Will definitely get back with pics before and after. Thanks a ton. 

Sent from my SM-G920I using Tapatalk


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