the GH should be easier to tell than the annoying KH test. you'd want a GH of about 5dGH or so for acidic conditions. you can easily tell when it turns from pale orange to green. if your GH is near 0dGH(as with pure distilled water from a store, you will want to increase it.) then the liquid might appear so pale orange that it may be hard to see when it turns green. if its turning green after a few drops, you'll need to raise GH. A healthy GH for your alkaline setup is 8dGH or higher.
What is your tap water?