JBL Test Kits are great for keeping an eye on the invisible properties of your water. Calcium, Magnesium, Silicate and Copper are just a few of the elements you can test for, in order to maintain excellent water quality. If certain substances build up, like Nitrates, you might find yourself with a difficult algae bloom to contend with, or worse you might start losing fish or coral. API know their business, and these tests are great for keeping control on your tank's levels.
Once you've tested your water, if you find that there are any negative chemicals present, these can usually be resolved with the use of appropriate treatments such as ammonia removers and phosphate and nitrate removers.