# Nitrates



## JRPW (2 Jun 2016)

Hi All,

Tanks looks kinda healthy with amonia and nitrites at near zero but my nitrates were at 80ppm before water change and then 40ppm after. Is that still too high? What should it be do you think?

Many Thanks
James


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## Aqua360 (3 Jun 2016)

JRPW said:


> Hi All,
> 
> Tanks looks kinda healthy with amonia and nitrites at near zero but my nitrates were at 80ppm before water change and then 40ppm after. Is that still too high? What should it be do you think?
> 
> ...



40ppm I've heard is good for plants, I wouldn't go higher than that if you have fish as well though


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## ian_m (3 Jun 2016)

Generally the lethal nitrate dose for fish is way over 1600ppm, so you have way to go yet.

After a pump failure I ran at 300ppm nitrate (and 80ppm PO4) for a while. Fish happy, plants happy, really annoyed as obviously cost a bit ofd wasted fertiliser and made s*d all difference to the plants.


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## xim (3 Jun 2016)

40 PPM after water change is still unnecessarily high, I figure no fish likes swimming in its own waste or the by-product of it. I would aim for 30-40 PPM before weekly water change. But there is a big caveat, can you trust the test kit?


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## Aqua360 (3 Jun 2016)

not to enter into debate, but there is suggestion that nitrates over 40ppm can damage larger fish such as Oscars over time; leading to infections such as HITH and such, I have no idea if that also extends to smaller fish though. Nor do I have the evidence or energy to argue for it lol


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## roundasapound (3 Jun 2016)

Mine is about 30ppm out of the tap! Still double dose EI macros and fish, shrimp are fine. I do a 65% weekly WC. According to the test kit it's something in the 160ppm by the end of the week. Deadly according to PAH. 
I'm considering tweaking my macro dosing only because if it saves money on adding nitrate then it's all good. But as for nitrate content in my aquarium water personally am not worried because I'm not seeing negative side effects to fauna. 


Sent from my iPhone using ️


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## alto (3 Jun 2016)

*HISTOPATHOLOGICAL CHANGES IN THE KIDNEY OF COMMON CARP, CYPRINUS CARPIO, FOLLOWING NITRATE EXPOSURE *



> *Abstract: *_Cyprinus carpio, _common carp was exposed to subleathel concentration (12 ppm) of nitrate (KNO3) under acute and chronic static bioassay conditions. The resultant histopathological changes in the liver were recorded by light microscopy. LC50 values of nitrate, according to Reed-Muench method, were 995 ppm for 48 hrs and 865 ppm for 96 hrs. For the acute tests, the fish were exposed to 12 ppm of nitrate for 1,2 and 4 days. For chronic tests, the fish were treated with 12 ppm of nitrate for 8, 16 and 32 days. Control fish were maintained in parallel with the experimental groups. Increase in Bowman’s space, degeneration of glomeruli, shrinkage of proximal tubule cells with pycnotic nuclei, increased tubular lumen and increased in intratubular hematopoietic tissue were the most significant changes observed in fish kidney after nitrate exposure. The effects were time dependent being more pronounced in acute treatments. The present investigation illustrates that presence of high concentration of nitrate in water are stressful to fishes.





> GENERAL OBSERVATIONS AND BEHAVIORAL RESPONSE
> 
> Acute and chronic treatment of fish with 12 ppm nitrate revealed substantial changes in fish behavior. These involved abrupt and sluggish swimming movements in various directions indicating an avoidance response. Occasional jumping and hitting the walls of aquaria were also noted.
> 
> As far as general condition of fish is concerned, rapid scale loss, especially from head region, was observed in acute treatment groups. These changes were more pronounced during the initial hours of exposure of fish to nitrate. Surprisingly, defecation by almost all challenged fish was recorded with in 30 minutes of exposure to nitrate Excessive secretion of mucous by treated fish was also observed which was particularly marked in the fish exposed to acute nitrate treatment where aquarium water became cloudy.



... nitrate doesn't sound quite so benign  

-  think I'll continue running my tanks at absurdly low nitrate levels  
Of course nitrate is not the only compound that will have increased in the aquarium, various organic compounds are generally elevated as well.

This article is not open access
*Acute and chronic toxicity of ammonia, nitrite, and nitrate to the endangered topeka shiner (Notropis topeka) and fathead minnows (Pimephales promelas)**†*



> Finally, the U.S. EPA's recommendation of a maximum of 90 mg/L NO3-N for the protection of warmwater fishes would protect Topeka shiners but not fathead minnows. For Topeka shiners, the MATC from the 30-d juvenile growth test was 360 mg/L NO3-N, but for fathead minnows, the MATC was 84 mg/L. More field sampling may be needed to determine if levels comply with criteria, especially in Topeka shiner critical habitat.


MATC = maximum acceptable toxicant concentration


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## micheljq (3 Jun 2016)

Be cautious, nitrates is a slow poison.  Fish can look healthy for months with 80ppm of nitrates then one day they stop feeding and eventually die.

If you have 80ppm nitrates, there is a problem, check if you do not overfeed, if the tank is not overstocked, if the filter is clean, not too much accumulation of debris, wastes in the tank, substrate namely, etc.

I keep mine at 10-20ppm.

Michel.


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## DanielC03 (3 Jun 2016)

micheljq said:


> I keep mine at 10-20ppm.
> 
> Michel.



What is the measuring method in which you base that statement?


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## dw1305 (3 Jun 2016)

Hi all, 
I like to keep the nitrate levels fairly low, but as others have pointed out it is <"really difficult to measure NO3- accurately">. Among aquarium keepers it is only really aquascapers who add NO3.

It is problematic to find scientific research that looks only at nitrate (NO3-), because most of the research measures the nitrate that accumulates from the microbial oxidation of ammonia (NH3/NH4+), or looks at pollution where high levels of NO3- are combined with high levels of orthophosphate (PO4---). 

The reason most research looks at nitrate as the "smoking gun" of (potentially) toxic levels of ammonia and nitrite (NO2) is that these compounds are transitory, but in the absence of  plants, nitrate levels can only be depleted by anaerobic denitrification, and out-gassing, as N2 gas. 

When you have plants the situation is different, they will convert NO3 into plant proteins like <"RuBisCO">. Assuming that other <"elements are available">, then plant growth and nitrogen levels are closely related.

Because of the difficulties in the accurate and repeatable measurement of many nutrients, I use the growth and colour of a floating plant as an indicator of nutrient level, and I called this the <"Duckweed Index">.

The rationale was that photosynthesis is driven by available light (<"PAR">), and after light by CO2 availability. Mineral nutrients are required in smaller amounts, with three macro-nutrients (NPK) and  about 10x as much nitrogen and potassium (K) needed as phosphorus (P). All the other nutrients are needed in lesser amounts.

Carbon dioxide availability isn't a problem for terrestrial plants (they have access to 400ppm CO2), but submerged plants are CO2 limited. You can use a floating plant to estimate nutrient levels because they have access to atmospheric CO2 levels and they are plants that are naturally adapted to utilise high light intensity.  

cheers Darrel


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## JRPW (3 Jun 2016)

Thanks all for the very detailed replies, will increase watwr changes a little just to be safe


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## Crusader58 (4 Jun 2016)

ian_m said:


> Generally the lethal nitrate dose for fish is way over 1600ppm, so you have way to go yet.



Where on earth do you get this figure from? everything I've read regarding general tolerance levels of nitrates for fish states 30ppm - 40ppm and for Goldfish, Koi etc as being even lower - at 20ppm - as safe levels. There are fish that are exceptions with tolerances much higher, but these aren't 'general'
1600ppm seems an awfully wide error margin.


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## ian_m (4 Jun 2016)

Crusader58 said:


> Where on earth do you get this figure from? everything I've read regarding general tolerance levels of nitrates for fish states 30ppm - 40ppm and for Goldfish, Koi etc as being even lower - at 20ppm - as safe levels. There are fish that are exceptions with tolerances much higher, but these aren't 'general'
> 1600ppm seems an awfully wide error margin.


As Darrel says inorganic sourced nitrate levels aren't nearly as toxic as organic sourced nitrates as organic sourced come with a lot of "extra baggage", nitrite, ammonia and other oxygen depleting organics, that all together cause toxicity issues.

A quick scan of potassium nitrate MSDS (material data sheet) reveals an aquatic LD (lethal dose to kill 50%) of 1400ppm.

So if nitrate source is plant food, you can run higher ppm without issues.


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## Crusader58 (4 Jun 2016)

ian_m said:


> As Darrel says inorganic sourced nitrate levels aren't nearly as toxic as organic sourced nitrates as organic sourced come with a lot of "extra baggage", nitrite, ammonia and other oxygen depleting organics, that all together cause toxicity issues.
> 
> A quick scan of potassium nitrate MSDS (material data sheet) reveals an aquatic LD (lethal dose to kill 50%) of 1400ppm.
> 
> So if nitrate source is plant food, you can run higher ppm without issues.


Exactly, the potassium nitrate can safely reach 1400ppm, but organic nitrates at those levels will almost certainly be fatal to fish in general.


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## xim (4 Jun 2016)

Just in case it is overlooked, the first example study in alto's post uses nitrate from KNO3. 
I have no idea though, about familiarity between the common carp and the fish we keep.


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## alto (4 Jun 2016)

Both studies use inorganic nitrate (salts) 



ian_m said:


> A quick scan of potassium nitrate MSDS (material data sheet) reveals an aquatic LD (lethal dose to kill 50%) of 1400ppm.




this is based upon some generalized (& likely outdated) study, don't use MSDS sheets except in a _*very*_ general sense ...
- the studies I linked give a far more realistic view of how nitrate can affect fish
When fish are placed in water with measurable nitrate levels, their plasma concentration of nitrate increases from virtually none to some measureable value, it's not just passive transfer across membranes however, fish metabolism does "_work_" to limit nitrate levels; despite fish attempts to maintain limited nitrate levels in blood, there are biochemical changes in addition to the grosser physiological changes noted in the Carp paper.


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## dw1305 (4 Jun 2016)

Hi all,





alto said:


> Both studies use inorganic nitrate (salts)


I'm firmly in the "low nitrate" camp, but there is some research that quotes levels in the hundreds of ppm NO3 as safe. This one is from the <"Zebrafish" journal>.


> Based on NOEC (no observed effect concentration) values, safety levels should be set at 1450, 1855, and 1075 mg/L NO3−-N to prevent acute lethal effects in embryos, newly-hatched larvae, and swim-up larvae, respectively. In the chronic bioassay, larvae were exposed to nitrate concentrations of 50, 100, 200, and 400 mg/L NO3−-N during the entire larval period (23 days). No negative effects were observed either on larval performance or condition at concentrations up to 200 mg/L NO3−-N. However, at 400 mg/L NO3−-N, survival drastically decreased and fish showed reduced growth and evidence of morphological abnormalities. Accordingly, a safety level of 200 mg/L NO3−-N is recommended during the larval rearing of zebrafish to prevent negative impacts on juvenile production.


 from "Acute and Chronic Toxicity of Nitrate to Early Life Stages of Zebrafish—Setting Nitrate Safety Levels for Zebrafish Rearing".

cheers Darrel


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## alto (5 Jun 2016)

But then contrast with this article

Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates


> *Abstract*
> Published data on nitrate (
> 
> 
> &lt;img height="17" border="0" style="vertical-align:bottom" width="36" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0045653504009993-si1.gif"&gt;NO3-) toxicity to freshwater and marine animals are reviewed. New data on nitrate toxicity to the freshwater invertebrates _Eulimnogammarus toletanus_, _Echinogammarus echinosetosus_ and _Hydropsyche exocellata_ are also presented. The main toxic action of nitrate is due to the conversion of oxygen-carrying pigments to forms that are incapable of carrying oxygen. Nitrate toxicity to aquatic animals increases with increasing nitrate concentrations and exposure times. In contrast, nitrate toxicity may decrease with increasing body size, water salinity, and environmental adaptation. Freshwater animals appear to be more sensitive to nitrate than marine animals. A nitrate concentration of 10 mg NO3-N/l (USA federal maximum level for drinking water) can adversely affect, at least during long-term exposures, freshwater invertebrates (_E. toletanus_, _E. echinosetosus_, _Cheumatopsyche pettiti_, _Hydropsyche occidentalis_), fishes (_Oncorhynchus mykiss_, _Oncorhynchus tshawytscha_, _Salmo clarki_), and amphibians (_Pseudacris triseriata_, _Rana pipiens_, _Rana temporaria_, _Bufo bufo_). Safe levels below this nitrate concentration are recommended to protect sensitive freshwater animals from nitrate pollution. Furthermore, a maximum level of 2 mg NO3-N/l would be appropriate for protecting the most sensitive freshwater species. In the case of marine animals, a maximum level of 20 mg NO3-N/l may in general be acceptable. However, early developmental stages of some marine invertebrates, that are well adapted to low nitrate concentrations, may be so susceptible to nitrate as sensitive freshwater invertebrates.



Agenda definitely impacts outcome 
- groups supporting aquaculture where high nitrate buildup occurs, tend to find fishes that show limited impact ... or perhaps much depends on how impact is being measured/determined 

There are some rainbow fish studies in natural habitats that tend to support the sort of data in the above linked article, but then one can also examine "channel catfish" studies in natural waters that suggest minimal impact of significantly elevated nitrate levels


Nitrate-induced elevations in circulating sex steroid concentrations in female Siberian sturgeon (_Acipenser baeri_) in commercial aquaculture



> *Abstract*
> Although nitrate is a ubiquitous component of aquatic environments, and has become a global pollutant in a variety of aquatic systems, it has only recently begun to receive attention for its ability to alter endocrine function. Aquaculture environments with limited water exchange often contain nitrate concentrations far in excess of natural environments, yet nitrate's impact on the reproductive health and endocrine function of commercially important species residing in these environments has not been investigated. Two experiments were conducted evaluating the effects of elevated nitrate on cultured Siberian sturgeon (_Acipenser baeri_). The first experiment compared the effects of a 30 day exposure to 11.5 ± 0.36 and 57 ± 2.18 mg/L nitrate-N concentrations on plasma cortisol (F), glucose, 17β-estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT) concentrations. The second experiment was similar to the first but evaluated concentrations of 1.5 ± 0.057 and 57 ± 1.52 mg/L nitrate-N. In both experiments, after 30 days of exposure to a given nitrate concentration, blood samples were obtained at time 0, and a portion of those fish were then placed under confinement stress for a period of 6 h to evaluate whether nitrate affects the associated stress response. The fish were bled at 1 h and 6 h during the confinement period. Results revealed that 57 mg/L nitrate-N exposure was associated with an increase in plasma T, 11-KT and E2 concentrations at time 0, but did not alter the associated stress response defined by elevated plasma cortisol concentrations. An additional measure of the stress response, plasma glucose concentration, however, was altered by nitrate exposure during the 6 h period of confinement stress in Experiment 1, but was not in Experiment 2. These findings demonstrate that nitrate has the potential to disrupt endocrine function and possibly secondary stress responses in cultured Siberian sturgeon.



As one might expect, biochemical data may differ significantly from data based upon behavioral observations or changes in growth patterns etc

But I'll stop flogging this poor topic now


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## dw1305 (5 Jun 2016)

Hi all, 





alto said:


> groups supporting aquaculture where high nitrate buildup occurs, tend to find fishes that show limited impact ... or perhaps much depends on how impact is being measured/determined


They certainly do. A lot of the problem goes back to accurate measurement, particularly at low NO3- levels in water with an unknown level of other anions (often Cl- or SO2--).

I'd really like to know what the real NO3- levels are in my tanks (and in everybody else's), but realistically it isn't going to happen.

I would also have some doubts about some of the published values in journals. I'm not suggesting scientific fraud, I'm just suggesting that one researchers reading of 10ppm NO3 isn't necessarily the same as another researchers, making a review of meta-data problematic. I also thing that is why published values for NO3 toxicity vary so much (through two orders of magnitude), in the really high cases it is quite possible that some of the ions measured weren't actually NO3, but another monovalent anion.

You have more chance of accurate measurement in marine aquariums, where there is a known amount of Cl- ions (27,000 ppm).

My personal thought are that for long term fish health low NO3 levels are probably advantageous. Bizarrely I also think they might be better for long term plant growth, purely because plants are nitrogen limited and grew more slowly. There is a summary here: <"Setting up empty tank.......">.

cheers Darrel


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## PARAGUAY (6 Jun 2016)

Maybe if not using RO using a Nitrate remover in high nitrate tapwater before the water change is a good option,assuming the utility company reading can be taken as accurate.Aquatic retailers have different opinions on fish and nitrate which is confusing.  Do we need to address our issues with external canister filtration more They are often described as Nitrate canisters.


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## dw1305 (6 Jun 2016)

Hi all, 





PARAGUAY said:


> Maybe if not using RO using a Nitrate remover in high nitrate tapwater before the water change is a good option,assuming the utility company reading can be taken as accurate.


Water companies use ion exchange resins to reduce NO3 levels, but you don't actually need a specific anion exchange resin, floating plants are as good, and a much cheaper option. You also have a negative feedback loop where increased nitrogen levels lead to increased plant growth, which reduces nitrogen levels etc.

Using floating plants to treat agricultural effluents is well established science. They  are described as FAMTS ("floating aquatic macrophyte treatment systems") in the scientific literature. If you go to <"Google scholar"> and type <"Floating aquatic macrophyte FAMTS nitrate"> you'll get over a thousand papers where floating plants have been used to re-mediate polluted waste water. If you look at <"vertical flow constructed wetlands nitrate"> you get over 20,000 papers.

In the EU the maximum permitted level of NO3 in tap water is 50ppm, and even though it is exceeded at times in SE England (and more frequently in SE Spain etc.) by and large the water companies have made efforts to <"reduce the levels of NO3 in tap water">. 





PARAGUAY said:


> Do we need to address our issues with external canister filtration more They are often described as Nitrate canisters.


Any efficient aerobic biological filtration system will produce enhanced levels of NO3, it just means that it has converted all the NH3/NH4+ and NO2- to the less toxic NO3. 

If you don't have plants you are reliant on water changes, ion exchange resins or anaerobic de-nitrification and out-gassing to remove nitrates. If you have plants you can just export your nutrients when you skim off the excess plants. 

If you use _Limnobium laevigatum_ as your "Duckweed" you may even be able to sell it on ebay or get a credit for it at your LFS.

cheers Darrel


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