Two Black Ghost Knifefish?

[Alan]

Hi

I've heard numerous times that BGKs should be kept either singularly, or as a group of more than three, because of potential aggro. But I was wondering whether a duo could be kept if they were a sexed pair, with enough tunnels for them to hide apart? I know that they need to be a reasonable size for them to be sexed; mine is a beautiful 13" female.

[Marc van Arc]

A single specimen will do fine, but a group is certainly no guarantee for success. I used to have 9 specimens in my 200x60x60 with plenty of hiding spaces, but within a year and a half there were just 3 specimens left and these kept biting each other's tails off.
I guess it is just a matter of trying and finding out.