Help with Yellow Tang behavior.

[Virginia Reef]

My Yellow Tang is about 5" long and is in a 90gal reef tank. I have had it for about a year. It appears quite healthy-good color, fins are normally extended, and quite plump. A couple of days ago it started acting a bit unusual. It is fanning the sandbed in a corner of the tank close to some LR. It has created a 2" depression in the 6" DSB. It does not appear to be scraping itself against either the LR or the DSB. Also, its white tail "scalpels" are noticeably extended. The fanning activity is a fairly forceful upward thrust from the sandbed which it is repeating pretty frequently. The Tang has been less active feeding on Nori for the past several days as well as on Blender Mush and frozen brine.

I also have a much smaller Longnose Butterfly that has peacefully coexisted with the Tang for many months. The Tang has always been the King of the tank. The Butterfly is now occasionally "displaying" its fins toward the Tang in the vicinity of the fanning.

The Tang has also been spending a bit more time than usual near my Cleaner Shrimp since the fanning behavior started. The Cleaner Shrimp do not appear to be doing any "cleaning."

Some of my thoughts are: 1) The fanning is a sign of distress-perhaps some internal (or invisible external) parasites, 2) The fanning and extended "scalpels" are a defensive posture toward the much smaller Butterfly, 3) There is some misguided spawning behavior either by the Tang itself or in conjunction with the Butterfly.

Any thoughts on this would be appreciated.

 

[mrrrkva]

Interesting behavior I dont quite have an answer for other than showing signs of aggression,
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