Iodine is essential trace for marine inverts. Source: reef-grade salt mixes (Reef Crystals, Tropic Marin Pro Reef, Red Sea Coral Pro, Brightwell Neomarine) all contain iodine at proper levels. When to supplement: heavy shrimp + snail + soft coral colonies that consume iodine faster than weekly water changes replace. Most casual reefs do NOT need supplementation. Forms: potassium iodide (most common, in Tropic Marin Iodine), Lugol's (10x stronger, dose-cautious), Brightwell Lugol's, Salifert Iodine. Dosing: match consumption to weekly water-change replacement. Use a Salifert iodine test kit. Target 0.06 ppm. Risk: iodine overdose burns soft corals + kills shrimp molts. Symptoms of deficiency: shrimp fail to molt, snails fade in color, soft corals look stressed. Caveat: ICP testing is more reliable than home iodine kits because iodine reads inconsistently.
Reviewed by the Fast Aquatics husbandry team · Updated May 2026
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