I have a pool ph test kit basically a vial and color coded setup. I cannot find a ph meter nor at this time can afford one. I know my tap water is 7.2 which from what i understand for a soil grow is pretty good. My question, is it possible to test after adding nutes with this kind of test kit? The reason i ask is the nutes change the color of the water. Is there a trick or do i have to break down and buy a meter?