I cannot distinguish yellows in OTO test levels 2-5 look the same to me. Any advice? I've seen you are supposed to look in natural light, but it is usually late by the time I get to test. Do you know of other quick tests that are easier to distinguish?
Can I use a ORP/pH meter instead? I saw one by Hanna instruments that looked simple to use. Do you have an idea how I could relate OPR values to ppm chlorine levels ?