Keep your fish healthy and thriving by testing your aquarium water regularly with easy-to-use API 5-in-1 TEST STRIPS. API 5-in-1 TEST STRIPS for freshwater and saltwater aquariums help fish owners measure levels of Nitrite, Nitrate, Carbonate & General Hardness, and pH found in aquarium water.In order for fish to thrive, water must be similar to that which could be found in their natural environment. Poor water quality can cause fish stress, illness, and even death. Just dip a strip directly into your aquarium and use the color-coded chart to determine if your water is safe, or if adjustments are needed. Then follow the recommendations to treat the water – it’s that simple.