Be confident in your purchase we're an Authorized Coral RX Dealer. How cool is that?!?!? Features: Accurately and immediately measures magnesium levels in aquarium water. Fintastic for managing levels of magnesium that promote healthy photosynthesis. Performs up to fifty accurate tests for repeated use. Changes color when it detects even minor fluctuations. Helps you maintain healthy water for aquarium setups. Your marine friends need safe, balanced water to grow and thrive in, so make sure their home is safe with the Salifert Magnesium Aquarium Water Test Kit. Fintastic for measuring the levels of magnesium in your aquarium?s water, this test kit can accurately and immediately perform checks up to fifty times, meaning you can rest easy knowing your pals are swimming in safe water for a long time to come. Balanced levels of magnesium are important for the health of your plant friends, so this kit can help you make sure they can photosynthesize properly. These tests change color to detect even minor fluctuations so you can find them early on for vital intervention as needed so your fish, plants, and other marine friends can swim about happily and healthily.