Your frontosa should be fine with the peacocks. I have a tank of frontosa with a few peacocks. The only problem comes at feeding time, the peacocks are much faster. Although, the frontosas have adjusted by creating a feeding frenzy at feeding time.
GL and hope he does good. Eating krill is good. Is it FD krill? If so I would squeeze it under water to get rid of any air , and allow it to sink. You don't want him feeding from the surface.