Phosphate can enter your aquarium through tap water fish waste and decaying organics such as uneaten food and dead algae. Excess phosphate contributes to unsightly algae and green water blooms and in saltwater excess phosphate can inhibit the growth of hard corals. The API phosphate test kit tests phosphate levels from 0 to 10 ppm so that you can easily monitor the condition of your aquarium water. May be used in both fresh and saltwater aquariums. We recommend that you take a few minutes each week to monitor your aquarium conditions and create a better underwater world for your fish. Testing your aquarium water has never been so easy or accurate. Contains 150 tests and includes 2 test solutions easy to ready instructions glass test tube and 2 color charts.