Many people cram tons of Africans together, especially mbuna.
The two I mentioned are not mbuna type that you would cram together like typical rift lake Africans, they live over sand substrate in shoals.
I grew a group of 6 Fossorochromis together in a 150 gal, 2 males hit about 12", females 8-10". The dominant male killed his brother, then paired up with one female, and I removed the rest.
After spawning she would cram 50 to 60 x 2" young in her mouth, a fascinating sight.
When startled they can dive into sand substrate and totally disappear, even though the males was a bright purple/blue .