I was also thinking of setting up a West African Biotope, to my knoledge plants such as Crinium natans and Bolbitus heudolti are present in these regions. If you're going to keep the common, peters elephant nose, I would suggest keeping them either on their own or in a group of 10 or more. In small groups of 3's and 4's there will be aggresion and bullying towards the smaller species.

Cheers,
Mike