Nitrate tests vary Api/Red Sea (help)

[Doughbwahh]

So I've been testing my nitrates. I do weekly water changes of around 20% in a 30 gallon tank. All of the fish and shrimp seem fine. I don't over feed (once every couple days). My nitrates don't seem to come down. The thing that's annoying me though is, I went out and purchased the Red Sea test kit...the readings were through the roof, so I had to do the high range test...looks to be about 64ppm. So I double checked with the Api kit, and it seems to be where it always has been (between 5-10) what's the crack with this? How can the kits vary so much? Seems a tad ridiculous that they vary so immensely!! :thumbdown:thumbdown

[cougareyes]

I'm having the same problem, Red Sea shows 5-10 and Salifert shows 50. I thought it was higher than 10 that's why I got the Salifert, maybe I should get the API as a tie breaker.

[Doughbwahh]

I'm having the same problem, Red Sea shows 5-10 and Salifert shows 50. I thought it was higher than 10 that's why I got the Salifert, maybe I should get the API as a tie breaker.

Yeah - I don't understand why they would vary so much? Seems a little bit ridiculous!

[fishchef]

I like Tetra NO3 tests. Easy to read. I've done Salifert and API.

[Sk8r]

I use Salifert. I had it read well over 100 after last fall's blackout, and I've fought it down over several months to Salifert's version of 10 or less. Whatever the tests say, my little montipora coral, an sps stony which I had bought as a bellwether of conditions, had closed up so completely that algae was growing on it and snails were crawling on it eating the algae. NOW it has shed the algae and will put out its fluorescent green polyps and color up a bit, which is the test I trust most. Today it added 'petals' to its polyps, which is what it should have. Corals like a nitrate of 2 or a fraction of 1. This is a vote I trust far more than any color strip. IT 'thinks' the nitrate is getting liveable.

[gbru316]

Red Sea is the only NO3 that I can detect a difference between the shades. API and salifert are worthless to me.

[bertoni]

Nitrate kits are fairly notorious for the wide range of results. I haven't found a good solution.

[Dan_P]

So I've been testing my nitrates. I do weekly water changes of around 20% in a 30 gallon tank. All of the fish and shrimp seem fine. I don't over feed (once every couple days). My nitrates don't seem to come down. The thing that's annoying me though is, I went out and purchased the Red Sea test kit...the readings were through the roof, so I had to do the high range test...looks to be about 64ppm. So I double checked with the Api kit, and it seems to be where it always has been (between 5-10) what's the crack with this? How can the kits vary so much? Seems a tad ridiculous that they vary so immensely!! :thumbdown:thumbdown

I have not used Red Sea (sorry) but have studied API and Salifert. API is formulated to read high nitrate levels and does not do well with low nitrate levels. It seems unable to detect nitrate around 1-2 ppm. Salifert is very good below 50 ppm, but above it is difficult to judge color differences. Your 5-10 ppm result though should be within API's useful range.

Comparing test colors to chart colors is a pain but would not account for a 10 v 64 ppm difference unless the chart colors are off as was recently reported for Salifert. Salifert is a very good test though.

Another reason for variation in test results is how well you mix the reagents. The reason is that some kits use zinc dust which settles out easily. Salifert soes not have this issue but API does. Maybe Red Sea does not use zinc dust. So, if you are not mixing the API reagent AND test solution very well, your reading will be low and variable. And if Red Sea like Salifert does not require vigorous mixing, you could be getting a true reading.

The only way to know for sure is to test a nitrate reference standard.

[Doughbwahh]

Thanks for all of the replies. I went to my lfs, who are awesome and always willing to help. They tested my water and said its below 5ppm. Which I am happy with. I told them about the Red Sea test and they also said that they have more problems with nitrates on that kit than anything else and told me to return it for a refund. They tested with salifert and Api. Each read less than 5ppm. Happy with that! :bounce3: