I've never used it myself, however, a friend did in his 120g reef tank. He had mixed results at first, then after almost 6 months of continued use started having water chemistry problems. After confirming his test results at the LFS, he was advised to discontinue use of Purple Up. Interestingly enough, after he stopped using it and started dosing calcium, alkalinity, and magnesium separately as needed (instead of all together with Purple Up, along with all the other ingredients in Purple Up), he had fewer water chemistry problems and his coralline algae growth took off, along with his coral growth.
