it has been my experience with test strips that they do work well with plain water. after i get my personal nute mix in the water it is no longer clear and that presents a problem with the strips. the drops have worked better for me but what i want to look at is the run off and i havent been able to do that accurately with strips or the drops do to the color of the run off unless it is after a good flushing. at present i need to bring the ph back up with my nute solution. starting with plain water at 8.5 ph add nutes and it drops to 5.2. plain water going in at 8.5 comes out of the soil at 6.3. as soon as they need nutes again i will check the run off and see what affect the nutes have on the ph in run off. my soil is pro mix bx with extra perlite added. i have some second run pro mix that was used for about 6 months then flushed real well and let dry be for reusing and so far it has not lost its buffering capabilities with plain water. still need to check after i add the nutes. thanks again fellas all input is valuble in 1 way or another.