Why does yellow tang get weird when...

I change out my activated carbon? None of my other fish act any differently. Clowns, gobys, blennys, inverts, coral... all good.

The yellow tang gets lethargic and hides in low flow spots when he is usually the exact opposite, only when I change my carbon out for a new bag?

When this first happened, I freaked out and did a good water change. I put the carbon in a few days later and it happened again... did the same. I did it one last time and this time it didn't act any different so I left the carbon in.

Well, it's time to change it so I did and tang went back to acting weird.

So what's going on? I bought a huge thing of Acurel premium activated carbon, is it bad? Can carbon go bad?

 

Carbon can change the clarity of the water. I imagine larger amounts added at one time change the ionic balance. Perhaps you working the tank makes the fish uncomfortable. Try added smaller amounts, try a different charcoal, perhaps try making the change at night. I would be really interested to see a follow up post on this topic.

 

How well are you rinsing it? The fines from the carbon could be irritating the tang.

 

Correct me if I am wrong, but wasn't activated carbon found to cause some HLLE issues in tangs?

 

Yes certain types were. I think Lignite based was the main culprit.

 

Yellow tang is swimming around eating like usual now after a small water change at night.

I did use a lot less carbon this time and rinsed it really good. I have used chemi-pure with no problems before which made me think I had some really cheap or bad carbon that was messing with my tank.

When I was able to use my last carbon bag, I kind of tricked the tang, did it at night when he wasn't aware and he acted normal in the morning last time.

I'll try a different brand of charcoal.