Hi allabouttheplants,
Welcome to TPT! I suffered for a couple of years with the API GH test kit and had exactly the same problem....it is difficult to see the color change even when looking 'down' into the test tube as they suggest. As I suffered the last couple of years I did some research for alternatives. Recently my API ran out and I purchased a SERA GH Test Kit from Aquacave ($10) and although it is not perfect it is 100% easier to read than the API Test Kit.
Welcome to TPT! I suffered for a couple of years with the API GH test kit and had exactly the same problem....it is difficult to see the color change even when looking 'down' into the test tube as they suggest. As I suffered the last couple of years I did some research for alternatives. Recently my API ran out and I purchased a SERA GH Test Kit from Aquacave ($10) and although it is not perfect it is 100% easier to read than the API Test Kit.