"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?

Hanna Instruments electronic colorimeter :-)
Goes down to 0.01 mg/l :-)