Can nitrates decrease during cycle?

[Soakem]

So im cycling my first tank right now and am almost 3 weeks into it. I've been doing test pretty regularly with the Red Sea multi test marine care kit.
My nitrite test maxs out at 1ppm and was at least that for about a week and a half. Today its finally coming down! I did a nitrate test as well and it also came down a little bit. All of the graphs that I see of the cycling process seem to have the nitrate going up pretty steadily but mine stayed at at 10ppm for about a week and then dropped to around 7 ppm. Can a drop in nitrates during this process be normal?

Thanks for any input.

 

[NY_Caveman]

Yes. I experienced the same recently. Likely due to denitrification (anaerobic conversion to Nitrogen gas).

 

[NY_Caveman]

It is a good, healthy sign.

 

[Soakem]

It is a good, healthy sign.

Awesome thats good to hear, thank you!

 

[Randy Holmes-Farley Verified Community Expert]

More likely than denitrification, it is interference of the nitrite on the nitrate value.

With many kits, a little nitrite can read as a lot of nitrate. As much as 100 ppm of nitrate for 1 ppm of nitrite.

So when nitrite declines (as yours did), nitrate appears to decline, but perhaps you have very little nitrate to begin with and it is just interference.

It's a dirty little secret that, sadly, nitrate kits rarely tell you.

 

[Soakem]

Would you recommend using a different test for nitrates other than the red sea kit?

Since the nitrate fell down to only 2 ppm when the nitrite came to zero would you still do the recommended a water change for cyclying?

 

[Randy Holmes-Farley Verified Community Expert]

Id recommend not measuring nitrate until nitrite is gone. [emoji3]

Once it is gone, nitrate testing is still fraught with errors and imprecision, but I do not have a specific kit I recommend and I don’t see a special reason to do a big water change.