Hi,
Is the Lombardoi the only fish in the tank?
If yes then my suggestion would be to get some more of them so you have 2, 8 ratio, and make sure you have hiding places i.e. rockformations or lots of pottery.
If you want more than one species then you should look into Metriclima Esthrea (Red Zebra)
http://www.thetropicaltank.co.uk/Fishindx/estherae.htm and make you composition something like 1, 4 of each.
You can also check out the other Mbunas but try not to get anything too aggresive, and something that does not resemble your current Lombardoi too much to avoid cross breeding.
My suggestion is also to avoid Demansoni and Auratus all together in a tank this size you will get alot of agression with these two Mbunas.
The Lombardoi is an Mbuna.
http://www.thetropicaltank.co.uk/Fishindx/m_lombardoi.htm