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I have a yellow tang that's probably five or six years old. For the past couple of weeks, he's been demonstrating some really weird behavior. He ducks under the live rock, holds himself parallel to the bottom of the tank and whacks at the bottom with his tail.

You can see that he's been doing this all over the tank, because where he does it, the sand gets pushed out of the way, leaving a bare spot -- and there are bare spots all over the tank.

I didn't really think he was sick, because he looks good, has been eating like a pig, etc., but I couldn't figure out what was triggering this weird behavior until I talked to the guy in my LFS about it. He suggested that the tang might be fighting with his own reflection in the bottom of the tank -- especially since he goes parallel to the bottom (but doesn't lie on it) and is basically doing nothing but hitting the bottom with his tail.

I suspect the guy was right, because when I got home, I tried putting some duct tape on the (outside) bottom of the tank to mute any reflection the fish might be seeing, and he pretty much quit doing it. (I would have just shoved some sand over the spot, but I couldn't reach under the live rock to do it.)

Anyway, do I just have a weird tang, or do other tangs do this, too?

The fighting with the reflection thing sounds pretty possible, but you said it was doing this in areas that already had sand? If that's the case, I don't see how the tang would be able to spot a reflection. Or does the live rock not have any sand underneath it?

If that actually is what is happening, it's not really abnormal. Tangs can be pretty intolerant of each other, and I have heard other stories of them battling mirror or tank glass reflections of themselves.

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

Hi there I agree with all of the above!
My yellow tang will fight her reflection if hang my jacket next to the tank because it's black when I take it away she stops immediately!
They are such intelligent animals but simple things like reflections seem beyond them

SW Pics: http://uk.pg.photos.yahoo.com/ph/dave_slade@btinternet.com/
Saltwater tank 125G-30G sump with caulerpa refugium.
yellow tang, atlantic anemone, 11 turbo snails, 4 nassarius snails, 12 various hermits, 3 cleaner shrimp, 2 occelaris clown, yellow

I think there were small bare areas underneath the live rock to begin with, as a result of gravel vacs, water currents, etc. The tang would then catch sight of a little piece of what he believed to be another fish, and start fanning his fins and thumping his tail at this apparent "fish," which flushed more sand out of the way and caused the bare spots. Or that's what I think happened, anyway ... all I can say is that he doesn't do it in any of the taped-over areas, and I've also never seen him doing it in an area that's completely covered with sand.

Why he started this now, however, after a year of being in my tank is a complete mystery ...

It probably grew in size and aggressiveness. Many fish, once settled in an aquarium for a while, begin to feel that all or part of the tank belongs to them. Most tangs act that way to an extent. They don't feel like competing for food (in this case, algae) with another tang. Your yellow just reacted in typical tang fashion. Since it decided that biting the reflection was impossible, it decided to stab it instead.

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

Having read this, first it doesn't surprise me that the Yellow Tang decided to attack its reflection, but second, it DOES surprise me that it found a reflection in such a strange spot!

However, it goes to show that unless you have a LOT of space, Tangs will become strongly territorial.

Having said that, if you take a look at the photos on the Practical Fishkeeping website of David Saxby's monster reef aquarium, he has eighteen Yellow Tangs living happily together ... but then his reef is a whopping 10 feet x 3 feet x 3 feet with a 2,400 gallon sump ... I don't know many other people who have three hundred fish in a single marine aquarium in the home ...


Panda Catfish fan and keeper/breeder since Christmas 2002