Flourish Nitrogen Plant Food?

Thanks for replying Dave, Its a 180ltr tank. On in the instructions for the
plant food it say's
that half of it is made up of nitrogen derived from nitrate, so I should be
able to test for nitrate and then double the PPM to find out how much
nitrogen is in my aquarium. Its also a little worrying for that reason. Does
anyone know if test kits can pass a use by date, as the one I'm using is
three years old?

"Dave S" wrote in message
...

"The Evil Hand" wrote in message
...
Hi, I recently started using flourish nitrogen plant food as the plants
in my aquarium stopped growing due to the nitrate level dropping to 0ppm.
On the label it says that it contains two sources of nitrogen, one being
from nitrate and that you can use a nitrate test kit to tell how much
nitrogen is in the tank by doubling the reading. But I am still unable to
get a reading using my Hagen test kit, even when I add the plant food
directly into the test tube?

Does anyone know why that is?

cheers
Evil Hand
What's the capacity of your aquarium?