Nitrates

[-Oscarmon-]

Today I got in a water test and had Nitrates at 5ppm-ish.

Here's the question: At which number do the nitrates become lethal?

I know it's toxic to begin with but let's say it's at 2ppm over a week. Safe?


Thanks in advance.

 

[Glenn238]

That's pretty low for nitrates which is good I don't let mine go above 20 ppm I'd say 40 ppm and above are when you will start to Run into problems

 

[Jexnell]

Lower is always better, with that said most try to stay at or below 20ppm.

 

[kno4te]

Even if not significany elevated. Some fish respond to elevated levels Chronic exposure to nitrates is never good as it’s not normally present. Sudden spikes in nitrates will cause issues. Anything over 50ppm needs to be fixed. The lower the better.

 

[Fishflyer]

Larger or more frequent Water changes will temporarily reduce nitrates by dilution. Also daily dosing of Prime or Safe might neutralize/convert toxins and help the bio cycle to move along and stabilize. Adding a beneficial bacteria culture. Adding additional or larger filtration system.
I might try to find the root of the problem if it is chronic. Quantity or size of fish as compared to Habitat size. A Cannister filter can help by adding more filtered water to your system.
Transfer out and distribute your fish among other tanks. Check for rotted vegetation, dead fish, deitrus from food/fish waste. Best of luck.

 

[esoxlucius]

One of the best analogys i've heard regarding nitrates and fish is to compare it to humans and cigarette smoke. Cigarette smoke won't kill you right away but you know that constant and heavy exposure to it will do damage you further down the road. Minimising your exposure to cigarette smoke will put you at less risk further down the road.

In an ideal world I think most of us would love to keep our nitrates around the 5ppm mark, and many do. And for others, myself included, we don't really like going anywhere near the red section on the ppi test card, which indicates that you're creeping into the 40ppm mark.

It's each to their own on this one but simply put, the lower the better.

 

[squint]

In scientific studies, it usually takes upwards of 4,000 ppm to kill fish. But on the Internet, 80 ppm is lethal.

 

[Drstrangelove]

No scientist will claim that nitrates are safe for aquatic animals. The only questions are what level, how long, what contributing factors, which species, and what ages. In other words, it's somewhat like aspirin, which is sometimes safe for healthy adults in limited amounts, but still dangerous and lethal in smaller amounts for children or infants, some adults, and in sufficient quantities, almost anyone under certain conditions.

The level that's lethal for nitrate depends on many factors such as age, species, duration, current health, etc. Levels as low as 2-3 ppm will kill eggs. Fry from some species can be impacted at below 10 ppm over time causing death. Amphibians and crustaceans can be impacted at levels that low.

It's important to note that controlled studies are not done on juvenile or adult fish exposed to levels such as 50 - 200 ppm for any extended periods of time, especially with any other contributing factors. E.g., studies don't look at what happens at say 100 ppm exposure for 30 days or longer.

Arguably, fish die indirectly for other reasons at these lower levels as nitrate exposure will reduce the effectiveness of the immune system and appetite. Long term survival or life span might also be reduced at levels that are even lower, but again, no studies have tested that.

Keeping aquatic animals in water with high nitrates is normally avoidable, so it's well worth targeting levels well below 40 ppm, and far lower for sensitive, long-lived, or rare species, and extremely low levels (below 5 ppm) for eggs and fry.

 

[squint]

It's impossible for science to convince aquarium hobbyists that nitrate isn't very toxic because no matter how long the study, hobbyists will always argue that it has to be longer. Nobody is going to conduct a 40-year study and even if they did, people would argue that it should be 60 years.

Not everything can be toxic but using the same arguments for nitrate toxicity, one can argue that anything is toxic.

Why aren't we as obsessed with phosphate toxicity, for example?

Note that most scientific papers use nitrate-nitrogen units so when they write 100 mg/L nitrate, it's really 443 mg/L nitrate.

The lowest numbers you see are for salmonid eggs and fry and range from 1.1-7.6 mg/L nitrate-nitrogen. That's 5-34 mg/L nitrate. Most of these numbers come from the 1979 Kincheloe paper which is regarded as unreliable. Those numbers are 30-day NOEC which will be much lower than 96-hr LC50.

If you look at other species and other studies, you'll see that guppy fry have a 96-hr LC50 of 191 mg/L nitrate-N or 846 mg/L nitrate. Of course, you'll just argue that the study wasn't long enough.

 

[duanes]

Agree with Drstrangelove.
I try to maintain my tanks at 2-5ppm nitrate concentration by doing lots of water changes, and using plants that consume nitrate, such as aquatic plants in tanks, emergent semi-aquatic in refugium/sumps) and Pothos.
Some fish eggs from spawning in my tank would not hatch at those concentrations, some would.
At that 2-5ppm concentration many fry of certain species would survive, some die off rate were quite high.
I believe although nitrate in the 20 and slightly above range may not be acutely lethal, it may over time have chronic effects, such as seen by the loads of HLLE posts and those oscars scarred that show up turned in to LFSs these and other species come from naturally low nitrate waters.
As part of my job, I used to do daily tests on raw lake Michigan water, the average result < (less than) 1ppm, which is also the case in many tropical lakes.
As an aside....
Did you do the test yourself, or take a sample somewhere to have it done? How long did it sit before testing?
These factors often determine a tests accuracy.
If a sample sits a hour or more before reagents are added, in the lab where I worked, it would be considered un-useable, and results not considered accurate.
As a sample sits its is going thru a host of reaction depending on its constituents.
A pH sample sitting more than 5 minutes would make the sample reading inaccurate, other water parameters tests have different holding times,