Question on the nitrogen cycle

[Thub]

Hi guys, I'm just finishing up my first ever fishless cycle, and I've been testing a lot more than during my previous tanks. I probably went a little off-book, in that I added 2ppm of ammonia from Ace hardware, along with some Dr. Tim's and then just left it.
Now that the ammonia is cycled out into nitrate, with just the faintest touch of purple in the API note kit, I was surprised to see between 5 and 10 ppm of nitrate. My first assumption was that 2ppm of nitrogen as NH3 would mean 2ppm of nitrogen as NO3, when the test appeared to show me I was wrong, i checked out the molecular weights of NH3 and NO3, and found them to be 18 and 80, which seems to explain the higher NO3 proportion. Am I right in that assumption?

 

[piranhaman00]

Yes 2 ppm ammonia will not produce 2 ppm nitrate.

 

[redfishbluefish]

You're not taking into account the nitrate that is leaching out of your rock. Just because you have nitrate doesn't mean your cycle is done. You should be able to add ammonia and "watch" it disappear. Typically you see nitrite for a bit while that bacteria works on populating your tank so that it can do it's thing to finally converting to nitrate.

 

[Psup]

Hi guys, I'm just finishing up my first ever fishless cycle, and I've been testing a lot more than during my previous tanks. I probably went a little off-book, in that I added 2ppm of ammonia from Ace hardware, along with some Dr. Tim's and then just left it.
Now that the ammonia is cycled out into nitrate, with just the faintest touch of purple in the API note kit, I was surprised to see between 5 and 10 ppm of nitrate. My first assumption was that 2ppm of nitrogen as NH3 would mean 2ppm of nitrogen as NO3, when the test appeared to show me I was wrong, i checked out the molecular weights of NH3 and NO3, and found them to be 18 and 80, which seems to explain the higher NO3 proportion. Am I right in that assumption?

All else remaining equal, 2ppm NH3 would equate to 7.3 ppm NO3. Using the equations of NH3 to NO2 to NH3. Im not posting the equations so as not to bore anyone

 

[Psup]

All else remaining equal, 2ppm NH3 would equate to 7.3 ppm NO3. Using the equations of NH3 to NO2 to NH3. Im not posting the equations so as not to bore anyone

Using the equations of NH3 to NO2 to NO3. Im not posting the equations so as not to bore anyone

 

[Randy Holmes-Farley Verified Community Expert]

Also note that if you have even 0.05 ppm nitrite, that can show in a nitrate kit as 5 ppm nitrate.

 

[Thub]

Also note that if you have even 0.05 ppm nitrite, that can show in a nitrate kit as 5 ppm nitrate.

That's... Interesting... Why is that? Is this true for freshwater kits too?

 

[Randy Holmes-Farley Verified Community Expert]

That's... Interesting... Why is that? Is this true for freshwater kits too?

I don’t know on freshwater kits, but for salt water, many convert a small fraction of nitrate into nitrite for detection and then multiply back. both Salifert and Tropic Marin have said they do this.

nitrate itself is a very unreactive molecule and is mist readily detected by converting it into more reactive nitrite.