So you going to buy a test kit and see exactly how much chlorine, ammonia, nitrites and nitrates you are going to expose your fish to? Are you going to test before each water change just in case the water supply varies? Seems like a big hassle to save a couple of cents per W/C, heck may even cost you more with the price of the test kit. Or you can just fly blind, especially if ya don't care if your fish suffer or not.