Hey N00dle
You can absolutely make a nice African cichlid tank out of your tank. That would be almost 30 US gallons - I'm guessing that your tank is 75cm x 30 cm or 90 cm x 30cm.
There are two options you can look at and I suggest continuing research before making a final decision, and deciding what is best for you.
You can do an mbuna tank from lake Malawi, but you must be very carefull with what species of fish you choose, most mbuna are too aggressive for that sized tank. Here are some species that I would recommend for you:
Labidochromis Caeruleus (AKA Electric Yellow, or Yellow Lab)
Labidochromis Perlmutt
Labidochromis Hongi
(choose only one labidochromis species, they will interbreed)
Iodotropheus Sprengerae
Pseudotropheus Saulosi
By keeping only one or two species you will have a mores successful experience.
The other options is a small Tanganyikan community. Get (one) pair of rock dwellers, (one) small harem or colony of shell dwellers, and a few dither fish.
Rock Dwellers: Look at Neolamprologus Leleupi, Neolamprologus Caudopuncatus, Julidochromis Regani, Julidochromis Transcriptus, Altolamprologus Compressiceps 'dwarf'
Shell dwellers: Neolamprologus Multifasciatus, Neolamprologus Similis, Neolamprologus Occelatus, Neolamprologus Brevis
Open Water: Any fast and tough open water fish will work
If you like busy, overstocked tanks, then the Malawi tank is the better option for you. If you like lighter stocked tank then Tanganyika is the better option.