Seachem focus reef and inverts safe ?

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Hi guys , so my 10 inch naso tang has been eating like a pig for 8 months but seems thin . Pinched stomach no matter how much he eats . So I assume it's a internal parasite , has anyone had experience with using seachem focus in a reef tank with no negative side effects ? Got 2 anemones and sps and Lps. I want to save the hassle of catching him and quarantine because he might not eat if I do. He currently eats from my hand and makes it easy to target feed him meds . Any advice would be great

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