Why are my nitrAtes so high?

[FastFly67]

29g planted tank, DIY CO2 diffused by a powerhead, 65W current USA, root tabs, dose with flourish. ammonia and nitrites both 0, nitrAtes are around 80 ppm. WTH? i've got danios, cories and snail.
i thought plants were supposed to slurp up nitrates. I lost my betta today (was in that tank) and a danio. Could this be the reason for the spike in nitrates?
Obviously I'm in the middle of a water change but I'm trying to figure out WHY they're so high to begin with.

 

[nurseashley]

test the water comeing from your tap. one place i lived i had city water and it was very high in nitRATES so no matter what i did my nitrates were high. I wound up buying bottled water....

 

[timwag2001]

i think root tabs nave nitrates in them but i'm not positive.

do you have a well? my water comes out of my well between 40-80ppm.
i cant tell the difference between the shades of red after 20ppm. anyone have a suggestion on nitrate test kits or maybe a cheap pinpoint probe for fresh water?

 

[fort384]

FF, What kind of fluorish are you dosing?

I too would start with checking the tap water....

 

[Purrbox]

What are your Phosphate levels? If your Phosphates have bottomed out this would prevent the use of the Nitrates.