# What is nutrient 'toxicity'.



## alan'67 (15 Dec 2016)

I have a limited knowledge of plant keeping and if you could see my tank you would agree!.

But, allowing for that, I've come to believe that giving aquatic plants the required nutrients was absolutely essential for long term success.

To achieve this, Tom Barr's EI method of a rich water column nutrient dosing regime (with a large weekly water change) seams to be the best and most successful method.

Many aquarium plant growers achieve great success this way.

But I have also read about something called 'nutrient toxicity' over the last 10 months and to be honest, I don't understand it.

I thought EI gave plants everything they could ever need under any circumstance and a large, weekly water change, re-set the tank parameters as it were.

So, if the above is correct, how can any nutrient in a planted tank become toxic?.


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## three-fingers (15 Dec 2016)

You are correct, nothing gets to toxic concentrations due to the 50% water change (and also the plants utilising the nutrients).

*Overdosing* some micros like iron or copper without the frequent 50% water changes could become an issue.

Unless you are vastly overdosing and not doing enough water changes it's simply not an issue.


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## zozo (15 Dec 2016)

alan'67 said:


> But I have also read about something called 'nutrient toxicity' over the last 10 months and to be honest, I don't understand it.



Here you have the whole package..  very well explained.
http://mtvernon.wsu.edu/path_team/P...Deficiency-and-Toxicity-Symptoms-MSU-2013.pdf 

In our case if you keep fish, your lifestock will be long dead before you will see any toxicity symptoms in plants.. What we need to be carefull with regarding lifestock is not put to much in it for the long term.. For example we aim at 20pmm maximum for Nitrate, tho to some fish sp. long term 20ppm N can be toxic others might take up to 80ppm before showing signs of distress. While plants will not be affected by these levels. Fish get weak and sick when exposed to long periodes to high concentrations..

But as for terrestrial plants and aquarium plants alike ferts are mainly disolved salts, i'm not totaly sure but i believe the high concentration of salt in the soil (or water column in our case) will be more damaging than the fert compount we try to add when overdosing.


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## ian_m (15 Dec 2016)

Due to a timer dosing pump issue I ran my tank with 320ppm NO3 and 80ppm PO4 for about a week. No fish deaths, no changes in plant health either. Really annoying as obviously was wasted money but made b*gger difference to the plants....


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## roadmaster (15 Dec 2016)

I started a low tech NON CO2 tank a few year's back with full EI and ran it for a few month's, before discovering I only needed a third of EI level's.
Toxicity would to me,,, assume Zero uptake by plant's,no water changes to export possible excess,and massive overdose of macro's or micro's far above suggested ranges for EI.(which are generous).
Even more disturbing is the fact that toxicity and or deficiencies sometimes share similar symptom's.


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## zozo (15 Dec 2016)

ian_m said:


> Due to a timer dosing pump issue I ran my tank with 320ppm NO3 and 80ppm PO4 for about a week.



Its all very relative, you wouldn't like to try that on your potted plants on the window sil.. I experienced with a wabi kusa, by mistake took the wrong bottle with KNO3 and water the plants.. Within a few hours it burned the crap out of them and it never was the same after that. Even after washing out the substrate with a few litres of clean water the long term effect was not beautifull, a lot died. In a water column this is much easier to correct obviously, and likely less drastic since plants metabolise much slower submersed. In terrestrial planst it's called "burn", so i assume the drastic results have to do with the difference of gass concentrations in the atmosphere vs watercolumn.


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## zozo (15 Dec 2016)

roadmaster said:


> Even more disturbing is the fact that toxicity and or deficiencies sometimes share similar symptom's.



As is explained in the link i posted above, that overdosing macros long term inhibits the plant to uptake some micros.. And obviously with diagnosing this wrongly you will spiral only more downwards with adding more micros instead of less macros.


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## roadmaster (15 Dec 2016)

zozo said:


> As is explained in the link i posted above, that overdosing macros long term inhibits the plant to uptake some micros.. And obviously with diagnosing this wrongly you will spiral only more downwards with adding more micros instead of less macros.


 
Problem as I see it,  is no one can tell you or me what level's are toxic in my tank's due to too many  variables such as source water,plant mass, types of plant's,light energy,substrate composistion,,to name a few.
Certainly too much of anything can be a waste or possibly detrimental.


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## zozo (15 Dec 2016)

roadmaster said:


> Problem as I see it,  is no one can tell you or me what level's are toxic in my tank's due to too many  variables such as source water,plant mass, types of plant's,light energy,substrate composistion,,to name a few.
> Certainly too much of anything can be a waste or possibly detrimental.



Yes it is very difficult, a year ago i had 15 Amano shrimps dying in 2 weeks time.. All turned ember color, showed eratic behaivor and finaly died. Water changes didn't help anymore once poissoned it is to late obviuosly. At least regarding the information i found via a german shrimp breeder site it was an obvious poisson symptom. They seem to accumulate it in some organ. Fish where not affected but all amanos except 1 died with the excact same symptoms. Never found out what substance poissoned them and very remarkable that one shrimp was unaffected and still lives today. I waited about 3 months before putting new amanos in which are also still ok today after half a year.. That was the first and fortunately the last mystery occuring in one of my tanks.


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## alan'67 (17 Dec 2016)

Thanks for your replies guys.

And I am going to save that guide zozo because I do find the hardest part of plant keeping is identifing the difference from one nutrient deficiency from another!.

Surely though even if by accident, a nitrate reading of 320ppm must have serious effects on overall tank health.


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## zozo (17 Dec 2016)

alan'67 said:


> Thanks for your replies guys.
> 
> And I am going to save that guide zozo because I do find the hardest part of plant keeping is identifing the difference from one nutrient deficiency from another!.
> 
> Surely though even if by accident, a nitrate reading of 320ppm must have serious effects on overall tank health.



A little mnemonic aid we all use is the difference in mobile and immobile fert deficiency symptoms. Mobile means ferts that can travel in a plant from old to young growth. When young growth looks healthy and older leaves show deficiencies it means a deficiency of mobile elements and the younger growth is sucking it out of the older growth. Immobile deficiency affects young growth as well. 

http://aquarium-fertilizer.com/aquatic-plant-deficiency


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## ian_m (18 Dec 2016)

alan'67 said:


> Surely though even if by accident, a nitrate reading of 320ppm must have serious effects on overall tank health.


Who says so ? I bet your local fish shop so they can sell you a nitrate test kit (£20) and nitrate away filter sponge (£20). £40 easy money for no need at all. The lethal dose for nitrates is in the 1000'ppm so 320ppm is not a lot. After all the max nitrate levels allowed in eu drinking water is 50ppm.


There are rumoured that long term higher levels of nitrate may cause issues but 320ppm shortish time clearly isn't an issue.


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## sciencefiction (19 Dec 2016)

alan'67 said:


> Surely though even if by accident, a nitrate reading of 320ppm must have serious effects on overall tank health.



It would have a serious effect if that nitrate was produced by the aquatic system in question in a relatively short period of time and not dosed in the form of inorganic fertilizers...Mostly perhaps due to low oxygen in such a system...

Some studies:
_Meade and Watts (1995) examined the toxic effects of NaNO3 on the survival and metabolic rate (oxygen consumption) in juvenile individuals (9–13 mm total length) of the Australian freshwater crayfish Cherax quadricarinatus. *After 5 days, no mortality was observed in cray- fish exposed to a nominal nitrate concentration of 1000 mg NO3-N/l.* Furthermore, no significant difference was observed in oxygen consumption between control (0 mg NO3-N/l) and experimental (1000 mg NO3-N/l) individuals (Table 1)._

1000mg NO3-N/l is roughly 4000ppm nitrates 

_Basuyaux and Mathieu (1999), studying the effect of elevated nitrate concentrations on growth of the abalone Haliotis tuberculata and the sea urchin Paracentrotus lividus during 15 days of exposure, reported maximum safe levels of 100 mg NO3-N/l for P. lividus and 250 mg NO3-N/l for H. tuberculata (Table 1)._

That is, 400ppm

_Knepp and Arkin (1973) reported that the channel catfish Ictalurus punctatus was able to tolerate a nitrate concentration of 90 mg NO3-N/l without affecting their growth and feeding activity after an exposure of 164 days_

Roughly 360ppm nitrates had no long term effect..

_Evaluating the short-term toxicity of NaNO3 to fingerlings (50– 76 mm total length) of I. punctatus at 22, 26 and 30 C, calculated 96 h LC50 values of 1355, 1423 and 1400 mg NO3-N/l
_
Mmm, there it goes...deadly to fingerlings at around 5600ppm 

Nitrate toxicity is largely dependent on fish species. Unless one keeps very specific and extremely sensitive species, what we aim in fish tanks is way below any nitrate toxicity levels for majority of fish. If one does a decent weekly water change, one should never ever worry about nitrates...

And some more from the same paper. Note how high these nitrate levels are...multiply each of those values by 4 to get the value our tests normally give....They are talking 1000ppm +

_Rubin and Elmaraghy (1977), after examining the acute toxicity of KNO3 to guppy (Poecilia reticulatus) fry, calculated 24, 48, 72 and 96 h LC50 values of 267, 219, 199 and 191 mg NO3-N/l (Table 3). Tomasso and Carmichael (1986) reported that the 96 h LC50 value of nitrate for the Guadalupe bass Micropterus treculi was 1261 mg NO3-N/l (Table 3). Tilak et al. (2002), using static and continuous flow through systems, determined 24 h LC50 values of 1565 and 1484 mg NO3-N/l for the Indian major carp Catla catla (Table 3). Scott and Crunkilton (2000), after conducting laboratory experiments to examine the acute toxicity of NaNO3 to larvae (<8 day old) of the fathead minnow Pimephales promelas, found that the 96 h LC50 value fell within the range of 1010–1607 mg NO3-N/l (average LC50 value of 1341 mg NO3-N/l; Table 3). Scott and Crunkilton (2000) also reported that the noobserved-effect concentration (NOEC) and the lowestobserved-effect concentration (LOEC), for the growth of newly hatched larvae (<24 h old) of P. promelas after an exposure of 7 days, were 358 and 717 mg NO3-N/l (Table 3). These larvae were lethargic and exhibited bent spines before death at a nitrate concentration of 717 mg NO3-N/l._

Further down below in the same study they start talking about ammonium nitrate which is a totally different ball game...

The accepted maximum nitrate levels recommended of roughly 2mg NO3-N/l and 10mg NO3-N/l (which is 8ppm and 40ppm nitrate respectively) is to protect the most senstitive species....ones which we do not keep in aquariums...

_Additional studies must also examine the influence of water hardness, salinity, pH, temperature, dissolved oxygen and other chemical compounds on nitrate toxicity to aquatic animals. Lastly, because aquatic organisms are subjected to biotic interactions (e.g., competition, predation, parasitism) and diseases, field and laboratory studies should be carried out to assess the effects of elevated nitrate concentrations on these ecological and evolutionary agents of natural selection.._

Source link: http://www.waterboards.ca.gov/water_issues/programs/tmdl/records/region_2/2008/ref2426.pdf


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## alan'67 (19 Dec 2016)

ian_m said:


> Who says so ? I bet your local fish shop so they can sell you a nitrate test kit (£20) and nitrate away filter sponge (£20). £40 easy money for no need at all. The lethal dose for nitrates is in the 1000'ppm so 320ppm is not a lot. After all the max nitrate levels allowed in eu drinking water is 50ppm.
> 
> 
> There are rumoured that long term higher levels of nitrate may cause issues but 320ppm shortish time clearly isn't an issue.



Ha Ha...... yes Ian you got me there, it was a LFS who said that.

But in his defence, he didn't try to sell me anything. And he is a experienced fish keeper (and a fan of the Walstad method) who has kept livestock for nearly 40 years.

And looking at his stock plus planted tank displays, I got the impression he knew what works ( at least for him).

I think his point was not high nitrates, Co2 , etc short term, but more about the effect of long term exposure at high levels to fish health, re-production etc.

But thanks to Sciencefiction's posted info above, (thanks for that mate) it seams that even at high tank levels there is nothing to worry about.


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## roadmaster (20 Dec 2016)

Hard to get close to high level's whatever you might deem them to be with 50% water changes once a week.
Raised many species of large south American cichlid's in fish only tank's with food's high in animal protein's at times.(organic waste)
Often might take two 50 % water changes a week to keep nitrates below 40ppm with uncalibrated API test kit.
No dosing scheme with mineral salt's like KNO3 I have seen, is going to render much worry bout Nitrates in planted aquarium's.
Too much food,possibly too many fishes,poor maint,likely to be more harmful over the long haul or on persistent basis.


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