Nitrate Testing in Presence of Nitrite

[Panda Jerk]

I’m was using lowly API testing for cycle, and today Nitrite tested ~2.0 so I tested Nitrate. API came back ~80 so I tried test with Nyos which was 95. So clearly there’s some Nitrate being detected, but is it being influenced by the presence of Nitrite? I read it somewhere, not sure if that’s really a thing.

I’m at day 19, Dr Tim’s fishless method. Ammonia at 0-0.5 about a week. Nitrite been hovering 2-4ish all week.

I feel like I’m prob cycled but wanted to see what people thought. I haven’t done the add 2.0 Ammonia to see what it reads in 24 hours (it’s tricky with work travel). I’ve been lights off the whole time, skimmer is on and it is pulling some gunk and turf scrubber is, well, wet, but no evidence of algae. There’s no typical algae bloom in the tank which I think is due to no lights being on, and only a light film on the glass. Basically, it looks like fill day with a little yellow tinge to the water.

I’ve never done this style of cycle, only the shrimp and (in the olden days) damsels, so I was a bit surprised my timeline did not track the Dr Tim’s guide. I was many days behind every step of the way it seemed.

Thoughts from the Homies?

 

[ryanjohn1]

Uglies are probably on the way. IMO toss in a cheap fish

 

[Idech]

Uglies are probably on the way. IMO toss in a cheap fish

Why does the life of a cheap fish matter less ?

 

[ISpeakForTheSeas]

So clearly there’s some Nitrate being detected, but is it being influenced by the presence of Nitrite? I read it somewhere, not sure if that’s really a thing.

Yes, Nitrate tests are influenced by the presence of Nitrite - Nitrites can cause ridiculously high Nitrate readings like you've found.

I've heard a lot of mixed results from Dr. Tim's lately, but to my knowledge the bacteria still works. You're probably cycled, but checking if the tank is converting ammonia quickly would be a safe way to verify that.

 

[Panda Jerk]

You're probably cycled, but checking if the tank is converting ammonia quickly would be a safe way to verify that.

Roger that. I’ll drop in 2.0ppm ammonia and test 24 hours later. Thanks for also confirming the influence of Nitrite on Nitrate readings.

 

[Randy Holmes-Farley Verified Community Expert]

Roger that. I’ll drop in 2.0ppm ammonia and test 24 hours later. Thanks for also confirming the influence of Nitrite on Nitrate readings.

The reason is related to the way most kits test for nitrate, which is hard to directly detect. Kits convert a small fraction of it to nitrite, then detect the nitrite, and multiply back up by the expected fraction that was converted to nitrite in the first step.

For that reason, a small amount of nitrite at the start of the test gets detected and multiplied up to give a false high level of nitrate.

The multiplier varies by kit, but can be 100:1 in some kits.