The Tetra EasyStrips 6-in-1 Test Strips measure six important water quality levels, nitrate, nitrite, hardness, chlorine, alkalinity and pH. The testing strips are fast, accurate and very easy to use. The testing strips are also safe to use in aquariums and are non-toxic. This product is safe to use in both fresh and saltwater aquariums or even use to test pond water parameters. The process is simple, just dip the strip into the water and read the results in just a few seconds. For new aquariums it is recommended to test your water daily and for established aquariums, test weekly.