Why wont my texas cichlid eat?

i got him last friday he's an adult texas around 7-8 inch and i got 2 jags when i got him also around the same time there in a 100 gallon tank water parameters are good but he just wont eat he has allready become the dominant fish in the tank witch to me is even more strange that he aint eating the jags eat like troopers tho any ideas ???