Seachem MultiTest Phosphate Fish & ; Aquatic Life Test Kit For more than 30 years aquarium hobbyists have turned to Seachem Laboratories for products designed by chemists and biologists. Seachem MultiTest: Phosphate is an easy-to-use kit that measures inorganic phosphate to less than 0.05 mg/L in marine and freshwater through an easy-to-read yellow-green-blue color range. Seachem MultiTest: Phosphate performs over 75 tests and has a reference s le for validation.