"Peter Pan" wrote in message ...
I've been using Aquarium Pharmaceuticals test kit to measure the Ammonia,
Nitrites, Nitrates pH ect.. After taking the prescribed measure of water and
using their solution, and waiting the appropriate amount of time, you
compare it to the color strip cards they provide to the color of the test
tube. I've been told by various people that you compare the color of the
tube to that on the cards, you should hold the tube up to the light and
compare that color to the color on the card. Others have told me to place
the tube directly on the card to compare the colors. You get dramatic
differences in the reading depending on what way you do it.

I would listen the manufacturer... :-)
I use these tests and I follow instructions and compare colors
holding sample vial over WHITE background. To get WHITE background
you CANNOT put the vial right at the color scale because your
will cause the white ambient light go through the color vial
once, then hit the white background coloring it, and go back toward
your eyes. In effect you are watching at the test tube placed on
the already colored background with the color light shining through it.

I keep the vial slightly elevated from the background, the way
the white piece of the scale is lighted with WHITE light...

If you put the vial right on the scale you should be reading
double concentrations to what is real, if you know what I mean.

I always get readings between the colors and I can never tell what I truly
have. Is there a better way to test the levels in my tank? Also what the
correct way to measure the colors against the cards.

To cure this problem, ask what color does your sister/wife/girlfriend
see - women have much better developed color recognition skills than men do.