Something is affecting my tangs and nothing else

[eddius_maximus]

Any idea what this is? I have a tank full of fish and they're all fine but my five tangs are all in distress. This is my unicorn tang and you can see the discoloration on his face. My Naso is also hurting although I couldn't get a picture of him. Yesterday I noticed the Naso was absolutely covered in black spots (black ich disease?). It looked like black dust covering his body. The black dust/spots are gone today and in their place, it looks like the Naso's skin is sloughing off. I wish I could get a picture but he's in hide mode.

All my tangs are exhibiting signs of sickness. Flashing, hiding. It's hard to tell but it also seems like their eyes are cloudy.

My other fish (clowns, rabbitfish, copperband, numerous wrasses, firefish, hawkfish, probably more I'm not thinking of) are all fine. My initial thought was velvet. But this has been happening for around a week now. Maybe I'm wrong but I assumed velvet would cause quicker deterioration.

 

[Redfoxtang]

Sorry to here about what’s happening right now. I think you have a number of problems going on right now. First if your seeing black spots on fish those would be worms a type of fluke. I believe a freshwater dip will help with this. Also I see what appears to be ich. Have fish been QTed? What are they eating?

 

[eddius_maximus]

Not QTed, a mistake I believe I'm starting to pay for. All of these tangs have been in this tank for a year at least, some much longer. Fat and happy, up until a week ago. They are still eating -- I make my own food consisting of scallops, oysters, shrimp, whatever looks good at the seafood section of my grocery store.

 

[Redfoxtang]

How many fish total in system? Something must have stressed these fish enough to have an outbreak. Have you added any fish lately and a change to the system itself?

 

[eddius_maximus]

350 gallon system, 29 fish. Most of them small. A few weeks ago I added a baby black mimic tang. I'm guessing this is what caused this. He was happy and eating and then one day just disappeared. I never found his body. No other system changes.

Assuming I can catch these tangs and quarantine them, what's the best course of action here? Tricky to treat for an affliction when I'm not entirely sure what it is!

 

[Redfoxtang]

I would pull all fish and out them in QT immediately. Couple 40g from petco I think they are having dollar per gallon sale. Get copper power dosed at 2.0ppm checked with a Hanna copper checker. That insures accuracy as color charts are hard to read. This needs to be done for 14 days then transferred for a sterile tank for observation. Meanwhile your DT needs to sit fallow for 76 days. No new addition for this time not even coral or inverts. This should give you the best chance for success!!

 

[eddius_maximus]

Your helps much appreciated!

 

[Redfoxtang]

If some fish are still showing black spots I would fresh water dip these fish for 4-5 minutes to relieve some stress off these fish. Also while they are in QT I would pick up Prazipro to help fight these worms off!!