Seriously Baffled By Nitrate Test Results

I'm currently fishless cycling 2 different tanks. One has live plants and driftwood in it, and the other has nothing in it except some sand on the bottom. I'm using the API nitrate test.

I had tested both tanks for nitrates about a week ago. The one with plants was at about 80ppm and the one with nothing was at about 5ppm. So on Sunday (2 days ago) I did an 80% water change on both of them. The one with nothing in it didn't really need it, but I figured I might as well while all the water changing equipment was out.

Monday (yesterday) I tested both for nitrates again. BOTH of them tested at about 80ppm. Both tests turned bright red. This is ONE day after doing a huge water change on both.

After the shock wore off, I tested my tap water for nitrates, and the results were 0ppm.

Thinking it must have been a mistake, I tested one of the tanks again today, and the test turned bright red again, showing ~80ppm.

I seriously do not understand. The only difference between the tap water and the tank water is that I added Prime to the tanks. What could have possibly happened?

 

Either your tap is high in nitrates (abnormally so, give some a test) or you're adding way too much ammonia. You need to test you ammonia and nitrite as well to know where your cycle is at.

 

OR, your second nitrate bottle wasn't shaken enough for the test to work properly. They say 30 seconds, but I would do 60 unless you're testing twice a day.

 

Following on from the above comment, I thought if you didn't shake the second nitrate test bottle enough it would give a false reading of 0, not really high?

Either way, as you've said you tested your tap water which read 0 I would make sure you're really shaking that nitrate 2 test bottle before you add to the test tube. If you haven't shaken it really well when you test your tap water, your tap water might not be 0 due to false reading.

Hope this helps good luck

 

If you've already did this many tests without shaking it then the reagent is toast as its an emulsion.

I suspect you're feeding too much ammonia and your test is fine.