Unless you enjoy doing testing, calibrating the test kits, calculating how to correct what the test kits tell you, etc. you are much better off using the test kit for a book end, and not testing. If you have a problem the plants will very likely tell you about it much more accurately than the test kit will. As far as I can see you don't have a problem, so relax, enjoy pruning the plants, watching the fish, and keeping those books upright with the test kit.