You don't necessarily need ammonia; you can do a fishless cycle using fish food and letting it rot down to produce the ammonia. If you want to keep Malawis, you should
defintely fishless cycle; you must overcrowd these fish to reduce aggression, so adding fish gradually is not really an option.
There are
lots of different species of African cichlid.
Pseudotropheus demasoni is a mbuna from Lake Malawi (not all Malawi cichlids are mbuna!).
It's not really my area of expertise although my mum keeps mbuna, but I believe they should have a 48" plus tank (a lot of places say 3 foot, but they are a
very aggressive fish; I don't think that would be big enough, even with the Demasoni's small size), and you need to keep
at least a dozen to reduce aggression.
As I said, you should post in the 'Old world cichlid' forum and get some proper advice from the experts; all Rift valley cichlids have quite specific requirements that you need to meet or you'll run into big problems
