from what i have read, your ph level should be above 7. also, they are omnivores-that means they eat plant and veggie material along with some proteins like krill and brine shrimp. i would get a good quality pellet (i use NLS brand food.. fish love it). i also read they WILL do well with other african cichlids like Malawians-they are very aggressive and can handle the malawi's lol. do not mix them with any other fish.
from what ive read, these fish are very aggressive. you will want that bigger tank and lots of rockwork for the females to hide in-the males are aggressive towards the females and they need places to hide. if you have a male, he may kill off a few females too-they are just aggressive fish lol
they get up to 4 1/2 inches long. the males are very colorful, but the females stay more of a washed out-drab color. once you find out how many males you have, if you have too many you may need to remove all but one and make sure he has a harem of females -you will want 3 or more ladies for him, that way he will not just beat up one girl, but will spread his aggression out..
btw, these fish are becoming rare to get-and close to becoming endangered! if you can get a good male, and a group of ladies for him try to breed them!
look at these links i found:
http://www.african-cichlid.com/Nyereri.htm
http://www.cichlid-forum.com/articles/p_nyererei_python.php
http://www.aquahobby.com/gallery/e_nyererei.php
http://www.cichlidae.com/section.php?n=ff&id=121
http://www.fishprofiles.com/files/profiles/259.htm