Why is my twinspot goby swimming?

[azreefgirl]

This morning I found my twinspot (4WD) goby floating at the top of the tank. Of course, I figured he was dead until I noticed his gills and fins were moving. He was breathing normally and not trying to get air from the surface. I turned on the actinics so I could watch him a little better (didn't want to shock him by turning on the pc's) and then he started to lower himself slowly. He reached the bottom and started moving around like nothing was wrong. So I turned on the pc's and fed everyone. He ate his mysis shrimp just fine so I left him alone. A few minutes later when I checked on him before I left for work, he was levitating about halfway up in the tank.
Has he all of a sudden developed the ability/fondness for swimming (which I doubt), or should I be prepared with the net when I get home?

He's been eating well and hasn't been acting unusual. Any ideas of what could be the problem?

 

[azreefgirl]

Went to lfs and explained his behavior to them. He's a signal goby: he's signaling. They said he was probably signaling for another goby. He may have caught a glimpse of his reflection in the glass and thought there was another one of his type around.
I feel so much better now knowing that this is normal behavior!

 

[lafresh]

Oh thank god! I've been searching online for an answer to this and finally found your comment. It makes sense since my goby kept swimming up against the glass quickly and stopping halfway, then swimming down like he was dead, letting the small current take him and then do it all again. Did yours end up ok?

Thanks