How do you tell the sex of Black ghost knife fish? I have 2 and they have started dancing round each other need to know if I should be moving all the other fish from the tank or seperating these two to keep the peace abit.

From aqua-fish.net

Sexing

There is no way to determine the sex of this fish just by looking at it.

couple of other side say the same

one even mentioned that it can change gender if appropriate, so you might have a couple there

But they are/can be aggressive to other tank members, I can imagine that will be worse while spawning

OOh crap Thank you the flatmate is now laughing becuase I was told these were 2 boys

oooh well more fishys maybe ....where to put another tank

it is pretty normal for them to zap each other, and "dance" circles around each other. keep an eye out for torn fins. I have housed more than 2 together, and they were awesome, and I didn't have any problems at all.

these guys have been happy together for months with the only occassional hissy fit nothing like this tho

could be the change in weather i.e. low pressure system approaching as fish are sensitive to this. I know my male fighters started blowing nests 2 -3 days ago so I knew before it was forecast that there was a colder front coming.