Salifert test kits are the epitome of accuracy and precision. Their wide range of available tests have all been designed to detect the smallest traces of certain elements, without interference from other chemicals within the water. Simply put, these are the best test kits you can buy- hands down. The sharp, contrasting color changes make results easy to read so there"s no second guessing. Trust your aquarium to Salifert. This test kit will measure ionically free strontium and complex, important for the accelerated growth of corals. This item not available for backorders.