I have a powder blue tang that has been slowly losing weight.  I got him from a fellow hobbyist, who had him for 3-4 months, and I have had it for at least 6.  So it's 10+ months removed from the wild.

A month or two ago I noticed that he seemed to be thinning somewhat.  He eats like a horse, and I feed a mixed diet three times a day.  He gets Formula2 Flake, Spirulina Flake, Nori, Mysis, etc.  I feed my herbs a heavy mix of algae matter, along with a smattering of meaty fare.  All other fish in the tank are doing fine, and there have been no new additions in 3 months or so...and these were QT'd.

A few days ago, I noticed that the tangs feces looks almost like he is passing flakes of aragonite sand.  It has been this way for a few days now, and I don't know how long it has been this way.

Any ideas?

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I would strongly suggest using a dewormer like praziquantel.  If your tang will take pellet food - I would suggest using a medicated food by Jungle which contains levamisole, metronidazole and praziquantel.  During this treatment, only feed the medicated food.

Please keep us updated on the tang's progress.

Best of luck.

Just ordered the Jungle food.

The blue tang was not initially QT'd by the original owner.  He had the fish 3-4 months before I got it...it's a 5"+/- tang, and he had it in a 65g tank.  It's much happier in my 300g.  The fish was very healthy when I got it, and since it had been healthy I moved it directly into my tank.

All of my fish go through a month long QT, and I run hyposalinity and feed medicated (bact & para) food for the first two weeks.  But, I have brought some new coral in so there is a possibility that something came in on a piece.

Will the Jungle food act as a dewormer, I'm assuming that it will.

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You could try adding garlic to the tang's diet.  Garlic does act as a natural dewormer.  Even if you do use the garlic, definitely use the Jungle food when it arrives.

Also consider quarantining everything wet - including rock, inverts, corals.

Let us know how the tang progresses.

Best of luck.

I only have dewormed in a quarantine/hospital setting.

Hopefully there will be more to chime in on this thread.

Thanks for contributing/sharing. 

My Jungle Anit-Parasite food arrived today, and it clearly says on the package "Not For Use With Saltwater Invertebrates".  So now I have to get the tang out of a 300g reef...where did I put those barbless fly hooks...that's right...I have a fish trap.

I'll let you know how things go.

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Thanks for sharing.

Best of luck - please update.

I am now feeding the remaining fish with garlic enhanced food and will watch for any problems among the rest of the population.

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Sorry about your loss.

I would recommend deworming all fish in your display as well as any future fish.

Thanks for sharing - again, sorry for your loss.