At the very least feed him as mash he can eat the day before you leave and then throw in some like red leaf lettuce for him to munch on if he gets hungry. He should be fine the whole week then.
I would slightly over feed it for a week before and then add lots of greens as dimondbacks said.
0.3.1 RES Holly 7.2" 8 years, Pine 7" 8 years, Preakness 3.75" 2 years, Clover 3" 2 years 1.0.0 EPT Bonsai 4" 15 years 2.0.0 Convict cichlid Mugger, Stripes 40 gal Preakness, Clover, Bonsai, Mugger 55 gal Holly, Pine, Stripes