Difference in Salifert and API nitrate test

[Randy Holmes-Farley]

Thanks - not surprisingly, my nitrite levels have fallen significantly today, and my nitrite fell way more than I expected - sitting at about 5ppm according the salifert test. I don't necessarily trust it but I was interested.

It's interesting that they don't mention this at all in their collateral. I wonder how many people not as fortunate as I to have this great forum have been tricked by this and have done all sorts of things to their tank to try to deal with a non-existent problem.

Well, that's likely the nitrite interference. Salifert has indicated that a little nitrite reads as a lot of nitrate, and with some kits, it can be 100x, so 0.25 ppm nitrite would read as 25 ppm nitrate.

 

[Dan_P]

My tank is 11 days old and I'm confused about the different nitrate readings I'm getting from my 2 test kits.

I used dry, bleached rock, which tested 0 ammonia, nitrite and nitrate after being in salt water for 8 days before I initially started my cycle.

To cycle, I used 100 drops of Dr Tim's ammonia in my waterbox 130.4 (total tank volume is around 430 taking into account rock, the recommended dose was around 400 drops), and added the recommended amount of Microbacter Start XLM. My ammonia got to 0.15 according to my Salifert test.

A couple of days later it had dropped to 0 ammonia so I re-dosed ammonia to 0.5. As you'd imagine, nitrate went up, I started seeing nitrate on day 4. By day 7, I was testing 0 ammonia, 0.25 nitrite and 25 nitrate. On day 8 I did a 20% water change and added 4 trochus snails, a tiny bit of GSP and an ugly acan frag my buddy was chucking out.

On day 10, ammonia was reading 0, nitrite 0.25, nitrate 50. I did a 30% wc.

Today, it's day 11. Ammonia 0, nitrite 0.25, nitrate 50 (or possibly even 100 on the Salifert test). I'm suspicious about this because I haven't fed the tank or added anything since doing a 30% water change, and before then was a bit of nori which I removed after about 20 minutes because the snails are too stupid to find it. I suppose it's possible the rock is leaching something, I guess. I'm running a skimmer, wet, and have a filter roller.

I used my API nitrate test and it's coming up 5 - 10ppm (honestly closer to 5). I ran both tests again; same thing, Salifert ~50, API 5. I watched videos making sure I'm doing the test properly and reading it properly. I am. I got my partner to do the tests, and he has got the same results.

Phos 0.03, maybe slightly clearer yesterday and today, but definitely more than 0.

I feel like I'm going crazy. Any suggestions?

You can‘t test for nitrates in the presence of nitrite. Nothing you can do. Just don’t do it.

API and Salifert nitrate tests give different values because they respond to nitrite differently.

 

[JimWelsh]

You can‘t test for nitrates in the presence of nitrite. Nothing you can do.

Sulfamic acid is commonly used to test for nitrate in the presence of nitrite.

 

[Dan_P]

Sulfamic acid is commonly used to test for nitrate in the presence of nitrite.

Does this accomplish the same thing as boiling the nitrite solution with urea and hydrochloric acid?

 

[JimWelsh]

Does this accomplish the same thing as boiling the nitrite solution with urea and hydrochloric acid?

I guess it depends upon what you mean by "accomplish the same thing", but they're two different approaches to solving the same problem.

 

[Dan_P]

I guess it depends upon what you mean by "accomplish the same thing", but they're two different approaches to solving the same problem.

Reduction of nitrite to ammonia.

What does sulfamic acid accomplish?

 

[JimWelsh]

Reduction of nitrite to ammonia.

What does sulfamic acid accomplish?

Converts nitrite to nitrogen gas.

 

[Dan_P]

Converts nitrite to nitrogen gas.

Great! Thanks.

 

[EeyoreIsMySpiritAnimal]

Converts nitrite to nitrogen gas.

And skips nitrate?

 

[Rmckoy]

*Also, while I'm in the camp that thinks API tests are fine, if you don't shake the living daylights out of the nitrate test solutions prior to adding them, and then shake the test tube really well, you might get a false reading.

(I'm talking banging the solution bottles on the table a few times and then shaking vigorously for a full minute... It's a real workout! Lol)

The test directions suggest shaking it “well” prior to doing the test .
Many of us have used api kits for many years . And trusted their results .
Getting the exact same results twice took some practice

 

[EeyoreIsMySpiritAnimal]

The test directions suggest shaking it “well” prior to doing the test .
Many of us have used api kits for many years . And trusted their results .
Getting the exact same results twice took some practice

I never said not to trust the results. Just trying to help brainstorm reasons why the OP had different results... ?

 

[JimWelsh]

And skips nitrate?

Yes. EDIT: Path #2 below:

 

[EeyoreIsMySpiritAnimal]

Yes.

Cool!

 

[JimWelsh]

Cool!

See my edit above.

 

[EeyoreIsMySpiritAnimal]

See my edit above.