i have a 30 gallon could i put a black ghost knife fish with my 2 columbian sharks or is there anything else i can put with them?

i use to have some columbian sharks however they died, but i do have black ghost knifefish which are AWSOME, another very weird but i think amazing fish is cuvier bichir, i have 2 of these and they are the best fish in my tank by far i love them to bits, they will eat anything which fits in there mouth so be careful thou. however i can not say how good these fish are its unreal, they are hardy and intresting to watch make sure you feed them just meat for them to grow to a fair size.
thank you

http://www.aquaticstoyourdoor.co.uk/Cuvier-Bichir.html