My two mandarins
 

Is this mating or fighting? The male has been in my tank for over a month and the female is new. I have uploaded a YouTube video. There is no mistaking that the female was biting the males back.

http://www.youtube.com/watch?v=QMFEfP0fnHw

Its hard to tell from the movie but it looks like they are both males. Do both fish have the spike on the front of the fin on the back? Mating happens at night they get together but never any aggression like that.

If their mating, its Broke Back Mountain style.

I think those are both males. When a pair mates they swim to the surface and join bellys and very gracefully glide back to the bottom.. Nothing aggressive like that.

Pretty sure they're fighting and you'll more than likely lose one of them. Most probably two males. This is the way they attack each other. Grabbing and holding and trying to force the other into a crevice. This was just explained to me the other day by a member who had the same thing happen.

:lol:

They like to rip competing males "spikes" right off as a show of dominance and to make them no competition in the eyes of a female.

this happens during shipping often and as a result, they can be hard to sex at the lfs.

The male is much larger than the female. If they are both the same size you may have a problem.

Fighting.

If they were mating, they dould be doing it in nearr darkness from my experience, and doing a spiral like move to the top of the tank.

Ken

Thanks for the help. It got more nasty but I managed to get the new comer out and I have a new home for him. It's a pity he was so docile, he even liked to rest on my hand....

They are fighting, and can't be kept together. You can try a social acclimation box like a recent thread descibes, but I'm pretty sure your "female" is a male. Some males take a long time to develop their dorsal spikes, and some never get spikes.