How long have you had it? Is it hosting a anemone? It could be Hypermelanization which is itritation caused by its anemone or host in which case nothing to worry about. If not, then black ich which would need to be treated with prazipro.
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Ryan.
300g with velocity t4 for return and a Reflo dart on a closed loop, T5 lights & SRO3000 skimmer.
Current Tank Info: 300g
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