# What causes a false (high) reading of nitrate?



## fishsandwitch (Apr 20, 2008)

Yo guys, I cant figure this one out. At the lfs I work at, a customer brings in water for testing. The nitrate is off the charts. It is blood red. (API test kit) The ammonia is 0-.25 and nitrite is zero. Tap tests at zero. This is happening on two seperate tanks. Water changes and gravel vacum every 2 weeks. Good filtration on each. What could cause it?


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## lescarpentier (Feb 2, 2008)

High bio load.
Dirty filters.

The readings are probably correct.
Mine tend to run high too.


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## spinycheek (Apr 26, 2008)

I would say the readings are also probably correct. If they are lazy about water changes (could be exaggerating the frequency of their water changes) and have no biological way to get rid of nitrates, then they can skyrocket. The aquarium I used to work at kept many of their marine tanks above 100 mg/L nitrate and some of the larger tanks were 300+ mg/L nitrate.

What are the bio-loads in the tanks?


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## fishsandwitch (Apr 20, 2008)

Everything points to it being an error. The tanks are not even half stocked. They have shrimp living in them. Good maintenance. One planted, one not. There is no way they are running at 200 plus ppm on nitrate


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## plantbrain (Dec 15, 2003)

And you have run a series of standards with your test kit or not?

If not.......... do not bother.
Every LFS should have a set of NO3 nd PO4 standards.

If anyone is to rely on your test kits and expertise............that is.

Then you can say something and not just assume or think the tap is really zero or not etc.

Even there, it does not matter, you need to see a reference based on the range in question, not the the extreme ranges:icon_idea

Regards, 
Tom barr


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## fishsandwitch (Apr 20, 2008)

I have not, but it is definitely reasonable accurate. When you test so many tanks it is easy to tell if it is off. We test our reef, planted tanks, all employee tanks, and it is easy to see if a test is off. I know it tests zero accurately because of testing RO water.


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## Homer_Simpson (May 10, 2007)

fishsandwitch said:


> I have not, but it is definitely reasonable accurate. When you test so many tanks it is easy to tell if it is off. We test our reef, planted tanks, all employee tanks, and it is easy to see if a test is off. I know it tests zero accurately because of testing RO water.


There is no question that a single huge water change will dramatically drop nitrate levels significantly. So tell the guy to bring in two samples of water. One prior to doing any water change and one after doing a 90% water change. If both those samples test ridiculously high for nitrates, then you have a serious issue with your test kits, cause there is no way that a water sample taken after a 90% water change should read anything close to a sample taken before such a huge water change.


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## lauraleellbp (Feb 3, 2008)

What kind of test are you using?

And has the guy brought in his tap water?


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## fishsandwitch (Apr 20, 2008)

API. This has been happening on multiple test kits, as well. (all api)
[email protected]


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## lauraleellbp (Feb 3, 2008)

Maybe he's being a little less than truthful about his tank maintenance...

If his tap water tests 0ppm nitrates then the solution should be simple; more water changes. I'd tell him to start doing 50% weekly and see where that gets him.

Plus clean the filters, trim the plants, and track down the source of that ammonia.


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## Wö£fëñxXx (Dec 2, 2003)

I agree, bet his tank is filthy.


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## plantbrain (Dec 15, 2003)

fishsandwitch said:


> I have not, but it is definitely reasonable accurate. When you test so many tanks it is easy to tell if it is off. We test our reef, planted tanks, all employee tanks, and it is easy to see if a test is off. I know it tests zero accurately because of testing RO water.


You missed the point here.
You still do not know what the range is at say 10ppm, 20ppm, 50ppm, 100ppm, 200ppm's, you only know that at 0ppm, it reads 0ppm.

Which are the ranges you are worried about here, not zero.This is why we test over a range, and also why you calibrate a pH/redox etc meter the same way(2 or more points of reference). You do not simply calibrate at a pH of 7 and that's it.

Which is what you are doing here with the API test kits.........and they have been wayyy off based on a dozen or more readings with folks here when they did calibrate them against a known standard. Try using Lamotte or Hach, those have been really good with calibrating solutions. I've suggested folks that do a lot of testing to use them going back to the early 1990's with good reason.

See LeftC's post on how to make some PO4 and NO3 reference solutions.
http://www.plantedtank.net/forums/water-parameters/47046-high-po4-no3.html

All you might need is a simple scale(20$ off ebay etc), the chemicals and that's pretty it with a larger solution. Then you can confirm and know what the NO3 and PO4 really is, no matter what test kit you are using. I have to do this and so does anyone doing research, even with a 20,000$ lab meter. Same stuff applies.

You can also ask the folks to freeze the samples, then you can thaw and measure the water over say several days to see what is happening in between water changes. They just freeze small 25ml samples each day or every other day etc.

Then thaw and measure all at once after you calibrate.
That reduces the times you need to calibrate.
I also agree with the other posters on their points.

Regards, 
Tom Barr


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## fishsandwitch (Apr 20, 2008)

I understand that, but its really not my choice. This is the only one we get abnormal results with. I would make them myself, but I dont bother testing my own aquariums.


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## Wö£fëñxXx (Dec 2, 2003)

This is what you do, you look the guy in the eye and you ask him
if his tank is nasty? how long since filter cleaning? properly!

Then you show him how to use test kit, or not, but sell him
one, tell him to go home, clean the filter one day, do a water
change the next, test. rinse and repeat until readings are lower.


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## plantbrain (Dec 15, 2003)

Wö£fëñxXx said:


> This is what you do, you look the guy in the eye and you ask him
> if his tank is nasty? how long since filter cleaning? properly!
> 
> Then you show him how to use test kit, or not, but sell him
> ...


Sounds good to me:thumbsup:
But they often will blame someone else and lie about their care(or lack thereof).

They fail on their own though, you cannot save and solve everyone's issues in the hobby. They have to to be willing to do the work.

You can also make/sell plant filters to remove the NO3.
Or algae scrubbers for marine systems.

Regards, 
Tom Barr


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## Wö£fëñxXx (Dec 2, 2003)

/off topic

Good to see you around Tom/ stranger


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## imeridian (Jan 19, 2007)

plantbrain said:


> But they often will blame someone else and lie about their care(or lack thereof).


but... but... that's the American way! Blame the problem on someone or something else, never take personal responsibility for your own action or inaction! :icon_roll

Anyway, I concur with everyone else, the tank in question is probably a nitrate factory.


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## plantbrain (Dec 15, 2003)

It's not just the American way, we all do it and do it a lot more than we think we do. We need to be aware of it and forgive ourselves, but also be honest.

I've had many clients that claimed one thing, then I tested it myself, only to find something quite different. Bottom line was they where looking for someone to blame for their failures. Having worked at the LFS a few years as kid, I saw it lot. I also knew what worked and what to do to rule things out.

Still, water changes cannot not be overdone and in most every case other than a few non CO2 methods, help a tank if the nutrients are added back and maintained.

So that's a no brainer. 
I think a reference solution at any LFS is mandatory or they carry better test kits that pass the muster such as Lamotte. This way the customer has more confidence in the results.

So they will look to you and come back to that LFS.
You will not find that service at Petsmart. You have to beat them at service, quality and advice because you are not going to beat Petco etc at price nor the on line vendors. Focus on reefs and planted tanks and other special areas that the large chains do not, that includes service/services/maintenace etc.

Regards, 
Tom Barr


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## fishsandwitch (Apr 20, 2008)

plantbrain said:


> It's not just the American way, we all do it and do it a lot more than we think we do. We need to be aware of it and forgive ourselves, but also be honest.
> 
> I've had many clients that claimed one thing, then I tested it myself, only to find something quite different. Bottom line was they where looking for someone to blame for their failures. Having worked at the LFS a few years as kid, I saw it lot. I also knew what worked and what to do to rule things out.
> 
> ...


Yeah, that is about what we do, but the truth is petco prices are not that good, we beat them on a lot of products. One is coming in soon to our town...but I dont think it will do much to us.


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