There are a lot of compatible species that would work in your tank, but of course as you already guessed there are plenty of problematic combinations as well! Working out your stocking plan in advance and asking those with experience is definitely the way to go.
A couple of questions:
What are the dimensions of your 50g tank?
Were you thinking about stocking mbuna or other malawi cichlids?
I would suggest taking a look at the following couple of links, doing a little reading, and picking out a few species that really catch your eye. Folks should be able to help you find a good mix of fish for your tank from there.
http
/www.wetpetz.com/lakemalawi.htm
While perfect by no means, this article adequately describes the three different types of cichlids commonly kept in aquariums from Lake Malawi. Mixing fish from two or more of these three groups can be done, but requires much more careful planning and knowledge than choosing fish from just one group.
http
/www.cichlid-forum.com/profiles/index.php?region=M
Just select Haps, Mbuna, or Peacocks from the Select the Subgroup dropdown for an extensive listing of species with links to information and pictures.
Hope that gets you started!
