Confusing Test Results for Ammonia API

[PNWAquatic]

Hi all! Sorry, a bit of a long post.

I was doing some routine testing and got some strange results.

First off, I tested my nitrates in my semi-new 15 gallon and the test came back at 0. This is odd because the tank is cycled and has previously tested 10-20ppm nitrate. I don't think it was a test kit or user error because my other tank had just tested at 5-10ppm nitrate a few minutes before. I also shook bottle number two vigorously and retested again with the same 0 results. Both tanks are densely planted but with relatively slow growing plants. The 15 gallon in question has java fern, Anubias, crypts and Vals (that are finally past their melting stage and putting up new leaves and runners, yay) and some duckweed.

Since I was already testing, I decided to run an ammonia and nitrite test on both of my tanks since I was already testing. Confusingly, both ammonia tests showed a slight green tint and looked closest to the .25 ppm test result. This is from both the newest cycled tank and an over a year old cycled tank. Thinking it may have been my tap water, I tested that as well and that came back the darkest green yet, potentially around .5. Nitrite was at 0 for both.

To be sure my results were accurate, I decided to run all three tests one more time and got 0 for both tanks and the tap water.

Finally, I ran the tests one more time 2 hours later and again got all 0s. In summary:

1st ammonia results for Tap 15 gallon, and 25 gallon: .25ppm.
2nd ammonia test results for tap, 15 gallon, and 25 gallon: 0ppm
third ammonia results for tap, 15 gallon, and 25 gallon: 0ppm

Because all livestock in both tanks are accounted for and behaving normally, I think I probably don't have any ammonia. My questions is has anyone ever experienced a false positive and discovered why for the API ammonia test? I did shake the bottles every time and gave them 5 minutes before checking the results. The kits have not expired yet. Also, what happened to my nitrate? Could the plants have used it all? I don't have any stem plants and my duckweed isn't really growing.

Thanks!

 

[Byron]

On the ammonia...if it is "x" in the tap water, it will enter the aquarium the same. The plants and/or nitrifying bacteria will catch up with it, so subsequent "0" makes sense. This doesn't explain the change in the tap water, though that may be due to who knows what in the source reservoir/water authority additives or whatever. BTW, if chloramine is added to your water, that may account for the 0.25 ammonia, as chloramine is a bond of chlorine and ammonia because the latter keeps the disinfecting capability while chlorine itself dissipates within 24 hours. I wouldn't worry about the ammonia results...but what is your pH?

On the nitrates. Are there fish in the 15g tank? If not, then the nitrates from the cycling (I am assuming that was the case) will disappear. Once fish are contributing organics, the plants will grab the ammonia and depending upon the fish load there may be little left for the nitrifying bacteria. So nitrates may remain zero (that would be nice for the fish!). It is true that the plants being slow-growing species are using less ammonia/ammonium, but again the fish load, water changes, organics all play into it.

When using the API nitrate test, Regent #2 has to be vigorously shaken for a good 2 minutes, not the 30 seconds in the instructions. Just to be sure.

 

[PNWAquatic]

I did get the .25ppm in both tanks before doing any sort of water change (last water change 3 days ago). The tap water also showed .25. I did check the water again only a few minutes later just to be sure and it was again back down to 0 for all three sources. A third test two hours after the first two tests also showed 0 for all three sources. I'm wondering what caused the positive the first time. I did not rinse the tubes before testing the first time so it is possible they were dirty.

Yep, I do make sure to really shake the nitrate bottles. I even hit it against a table a few times just to make sure. It still registers at 0. It is stocked with 8 Neon Tetra and nothing else (After reading more about the species, I understand 15 gallons is a bit small for neons. I am hoping to upgrade later). They've been in the tank for a month now. I had some annoying diatoms at first but those have gone away I think as the plants started taking up the nutrients better.

I have strange water I think. I have high pH (7.8) but soft water (my gH and kH I think are low). I found a report that says my KH is 1.152 dKH and my gH is 1.1 dGH if that makes sense.

 

[Byron]

I did get the .25ppm in both tanks before doing any sort of water change (last water change 3 days ago). The tap water also showed .25. I did check the water again only a few minutes later just to be sure and it was again back down to 0 for all three sources. A third test two hours after the first two tests also showed 0 for all three sources. I'm wondering what caused the positive the first time. I did not rinse the tubes before testing the first time so it is possible they were dirty.

Yep, I do make sure to really shake the nitrate bottles. I even hit it against a table a few times just to make sure. It still registers at 0. It is stocked with 8 Neon Tetra and nothing else (After reading more about the species, I understand 15 gallons is a bit small for neons. I am hoping to upgrade later). They've been in the tank for a month now. I had some annoying diatoms at first but those have gone away I think as the plants started taking up the nutrients better.

I have strange water I think. I have high pH (7.8) but soft water (my gH and kH I think are low). I found a report that says my KH is 1.152 dKH and my gH is 1.1 dGH if that makes sense.

Yes it does, I just noticed you are in Oregon. If that is western Oregon, you will have very soft water which is the same up through western Washington and into SW BC where I am. We are in soft water fish heaven!

They likely add something to raise the pH, they do up here, as an acidic pH (our reservoirs have a natural pH below 5) can corrode pipes. I have soda ash added, which dissipates out in a day or so. Check your water authority's website, it may say. And while there, see if they are adding chloramine; this could explain the ammonia.