Aquarium Water Test Kits
An aquarium test kit will help you monitor your water. All aquarium owners should use different tests to help adjust the water to your fish's individual requirements. Other types of tests may be recommended depending on your individual aquarium and the fish you keep.
Some pet shops will perform simple tests for you. Take a sample of water to your local store and many will tell you the current pH of your aquarium and recommend any corrections your fish need.
Generally dry tablet test kits will have longer shelf life than those kits using liquid regents but it will still be many years until expiration if stored by the manufacturer's directions.
Aquarium Water Reading
Aquarium Water Guide