Natural seawater (NSW) concentration of iodide is 0.06 mg/L. Ideally, it is advisable to maintain iodide close to NSW concentration. Concentrations above NSW may not be harmful, and, within limits, may even be beneﬁcial, but maintenance at elevated concentrations should be considered experimental. The innovative MultiTest™ Iodine/Iodide kit offers a quantitative test for this important element of soft and hard coral growth. It measures iodine or iodide to less than 0.005 mg/L. The color scale peaks at 0.10 mg/L. It performs over 75 tests and contains a reference sample for validation.