Just in case you didn't take this into consideration!
Try cleaning your instruments with hot destilled water and completely
esterilize even the pipet or syringes with clean water. Personally I even
dry it with alcohol to get rid of any humidity left.
If you use pure water, not tap, to zero your kit, there shouldn't be
anything to read. If you still get a reading then your chemicals are
polluted.
You should always get a reading, never zero, using your tank's water.
iy

"KurtG" wrote in message
.. .

I don't think my Red Sea Phosphate test will go under .1 ppm. I've tried
it with distilled water and I still get the 0.1 ppm. It seems to be the
color of the reagent the comes out of the bottle.

Any recommendations?

--Kurt