I think that he wants to know some good Black Ghost Knifefish tankmates (???).
If so, any of the bichir species would work (go for Senegals!), as well as spiny eels, and any of the larger species of schooling fish (i.e. high-backed tetras and barbs, bala sharks, ect. Depends on the size of the tank).
Cheers,
GobyMaster