I don't have experience of mixing convicts and africans...but I'm thinking if the convicts are breeding...smaller africans might be toast...and any african big enough to stand up to the convicts will kill 'em...but it is a 90 gallon tank...
ahh the breedin pair of convicts and african cichlid cross.... this is a hobbyest worst nightmare, we had to keep a few african in a 120 with two convicts for a while down at the store because the african cichlid tank cracked when one of our employees bumped a metal ladder against the glass. but the convict killed over half of them within a day.but then a selectric blue johanni cichlid ate all of the convicts fry and they went insane and chased every one around the tank the best advice i can give is if the convicts start spawning get a divider ASAP!