Nitrates Tested Salifert vs. API

[LBDave]

I have a 120 gal tank with a high bio load and quite a few plants. Oscars, pbass, silver dollars, geos and pleco.
I have been getting some low nitrate readings with the API test kit so I got a Salifert to vet it out.
Last week the tank was a mess after about 5 days. Lots of feeding and messy foods. Got my test kit and away we go!
The attached photo shows the tank about 3 months ago. Amazon swords are a little chewed down and tank has some hornwort now.

When I did this test I was very careful to follow the directs to the Tee. I am thinking that when I tested previously I did not shake up the API test solution and vial with the API kit enough.

1. Tested with Salifert and wow. Nitrates were 50 or more!
2. Tested with API and sure enough, Nitrates were 40 or more. A little hard to distinguish 40 - 80 difference.
3. Tested my tap water. Looks to be 0.
4. I did about a 60% water change and it loos like Nitrates are about 5 - 10 with the API kit.

Conclusion - Both kits show a high Nitrate reading for the tank before the water change. When the Nitrates get high it's a little hard to know how high with both kits, but the API is good at "flashing the red light" so to speak when Nitrates are high. Both indicated Nitrates were maybe 50. The Salifert results were really concerning as difficult to see how high.
The API was a little better at this. Bottom line both kits seem to work. I think I was shaking the stuff enough (API) in prior tests.
Tap water looks good. BTW I tested the tank again the following morning (fish not fed during the gap between tests). It looked the same as #4.

 

[esoxlucius]

I use API and although I find it a good test kit it used to infuriate the hell out of me that there is basically no difference in colour between the oranges of 10 and 20ppm and the reds of 40 and 80ppm. But I turned that to my advantage. Nowadays I just go with the train of thought that anything orange is reasonably acceptable and anything red is bad. If you try to distinguish between the oranges of 10 and 20 and the reds of 40 and 80 you'll end up going bananas.

 

[thebiggerthebetter]

My current understanding of at-home testing for NO3 nitrate is based on what dw1305 on Planet Catfish posted on the subject. Darrel is a professor and a scientist studying wastewater treatment in addition to being an avid tank keeper.

In a nutshell, API and other home tests can give an indication of the nitrate presence but the actual levels can be up to 10x higher and vary depending what other ions are present in the water being tested because those ions interfere with the measurement to a highly variable degree; also the toxicity associated with such high levels of nitrate often stems not from the nitrate itself but from the preceding nitrite and ammonia.

To begin learning, I'd recommend reading Darrel's posts in these threads and the links he and others (such as TwoTankAmin who is well versed too) provided therein:

ammonia nitrite and nitrate study - PlanetCatfish.com

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

High Nitrate - PlanetCatfish.com

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

water changes controversy - Page 2 - PlanetCatfish.com

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

 

[Coryloach]

If you are interested in reading about nitrate further I'd recommend this old thread:

Water Changes...Unnecessary?

So we know the purpose of water changes are to reduce nitrate levels in a tank or pond...but I always thought it was to also dilute the organic matters in the water(oil from food, fish urine, etc.) My tap water has 40ppm of nitrates to begin with, so am I wasting water & money if I perform a...

www.monsterfishkeepers.com

 

[LBDave]

Rule number 1 - Change your water often. Ask any discus owner.
Rule number 2 - If using a test kit follow the directions to the letter. Not sure if this is why I was getting lower readings before or not.
Rule number 3 - Test you water as often as possible. Suggest a few days after you change water.
Rule number 4 - Change your water often.

 

[DRC]

My current understanding of at-home testing for NO3 nitrate is based on what dw1305 on Planet Catfish posted on the subject. Darrel is a professor and a scientist studying wastewater treatment in addition to being an avid tank keeper.

In a nutshell, API and other home tests can give an indication of the nitrate presence but the actual levels can be up to 10x higher and vary depending what other ions are present in the water being tested because those ions interfere with the measurement to a highly variable degree; also the toxicity associated with such high levels of nitrate often stems not from the nitrate itself but from the preceding nitrite and ammonia.

To begin learning, I'd recommend reading Darrel's posts in these threads and the links he and others (such as TwoTankAmin who is well versed too) provided therein:

ammonia nitrite and nitrate study - PlanetCatfish.com

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

High Nitrate - PlanetCatfish.com

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

water changes controversy - Page 2 - PlanetCatfish.com

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

I came across this post looking for recommendations for an accurate way to test for nitrates, because I wasn’t too sure about my API readings (and yes I do all necessary shaking of bottle #2 and the vial). But after reading these articles, I’m like OK, never mind.

 

[thebiggerthebetter]

I came across this post looking for recommendations for an accurate way to test for nitrates, because I wasn’t too sure about my API readings (and yes I do all necessary shaking of bottle #2 and the vial). But after reading these articles, I’m like OK, never mind.

An absolute measure by API at home is impossible and the number obtained can easily be off by an order of magnitude. Good thing the nitrate toxicity begins in the thousands of ppm. But I think for a relative measure, it is good, if nothing else changes (same water source, same diet and amount, same substrate and biomedia, no medications added, etc.)

Professor Darryl (from my links) uses a dickweed index (how quickly duckweed multiplies) for an indirect but excellent relative nitrate measure.

 

[duanes]

The purpose in testing nitrate (for me) on an established aquarium, is to determine how often water changes should be done.
If I change 25% of the tanks water, and in a week, nitrate is already at 50ppm, it means to me, too much time has gone by between water changes, and not enough water was changed.
So instead of a once per week water change, that 50ppm reading tells me I need to change more water at least twice per week.
Or if my goal is a stable tank environment, for example, a constant 5 ppm nitrate as a ceiling. I might have to change 40% every other day .
Same with pH, if my tap is 7.5 pH, but after a week the tank water has dropped to 6.0, it means too much time has gone by, and the nutrients in the water have acidified it more than I feel is healthy, and to have a stabile tank, I need to change water more, and more of it.
pH is a little tricky, if you have plants because pH will fluctuate normally day and night.
S taking and testing for pH the same time of day is a way to determine stability.

 

[tiger15]

I have used both API and Salifert test kits. When API is fresh and you shake solution2 hard, it will give comparable results to Salifert. Over time as API solution2 is aged, the test concentration is off due to non uniform dispensing in the past, API test results are no longer comparable to Salifert. Salifert uses powder for the second test agent, so the concentration won’t change as long as you measure a correct level cup full of the agent. So Salifert will give you consistent results throughout.

API color chart is a joke. If 10-20 and 40-80 have identical color, why not label with two colors instead of lying with four colors. Salifert doesn’t lie about the color resolution, and has a refined option to read lower concentrations. So my conclusion is Salifert gives more consistent results and is not sensitive to shaking and aging. Without comparison to lab results, I am not able to assess which one is closer to the true nitrate concentration, just one is more consistent and thereby more reliable than the other.

As to nitrate harm to fish, don’t be alarmed to see high nitrate concentration if you have a heavily stocked tank as long as you do frequent WC. Nitrate is a proxy indicator of general pollution of many unknown and untested pollutants. Nitrate up to 100 ppm has been demonstrated to be harmless to fish in planted tanks where the source of nitrate is principally from dosing nitrate fertilizer. I dose about 20 ppm of nitrate after each weekly 75% WC in my planted cichlid tank. The stocking is so heavy that the pre WC nitrate is in the 40 ppm range despite plants stripping nitrogen.

 

[Coryloach]

The best and easiest way in my opinion to measure pollution is still a TDS/Conductivity meter, especially in non-planted tanks where there is no fertilizer dosing. I can't remember testing nitrates for 4-5 years or so and I got the last test just so I do a random check if my "TDS theories" are working.

If one goes by a stable TDS tank vs tap, doing enough water changes to maintain it, there will also be no nitrate rise. In a planted tank the TDS can actually drop further than the tap water, so does the nitrate....

See, if you don't monitor the TDS, that nitrate test maybe telling you the tank has 15ppm nitrate but your TDS could have become double your tap water, meaning pollution has accumulated regardless. Nitrate is just one pollutant..

As @thebiggerthebetter is pointing out in his above post, the nitrate test may not give the true nitrate level. It may be way higher than what the color chart suggests...giving you false confidence. Then one thinks their water quality is fine and contributes their latest fish death to "mystery".

If one is stuck into the nitrate testing, test both nitrate and TDS for a while and see how those are related for yourself..You may notice that your "safe nitrate" levels aren't preventing a TDS rise. The TDS meters sold measure conductivity, i.e. ions dissolved in water including nitrate.

Generally, if the TDS is in line with tap water, so are all other parameters, KH, pH, GH, etc...although you don't know their exact levels and you don't know the exact break down of what the TDS test gives you, you know they're in line with your water used for water changes, which is what matters to the fish health.