Hippo Tang scratching against rocks?

[meskin]

Just got a beautiful new hippo tang yesterday, about two inches long, and no visual signs at all of ich or anything else on his skin. Smooth and blue. Swims all over and eats like crazy (formula b, mysis, pellets, seaweed, etc.). Tank levels are all good (Amonia 0, nitrite 0, ph 8.2), with only the nitrates a bit elevated (25). My concern is that he is CONSTANTLY and purposely scratching himself against the edges of the live rock. He'll pick a spot he likes, and swim past an edge of the rock 10, 15, 20 times in a row, "wiggling" against the edge of the rock. It looks like he's either (a) got an itch he can't seem to scratch, or (b) trying to shake stuff off the LR to eat. Should I be concerned that something is wrong, or is this normal behavior for a hippo tang (or at least one in a new environment). Thanks.

[New to the reef]

I think it's stress. My yellow tang did it for a week or so after I got him.

[zma21]

Could be a sign of oncoming ick.

[reefergeorge]

Is he in quarantine or your DT? If he is in quarantine you can lower your sg to 1.009. He could have ich in his gills and you will never see any spots.

[meskin]

Main tank unfortunately (93 gal. with lots of LR - about 160 lbs, 5 fish, 5 snails, 5 hermits). Any fish are impossible to catch in this tank, other than perhaps the clown, which seems to like playing with the net...