If you want your bichirs to look fat then just keep feeding and feeding, simple as that. Plenty of sea foods in the fish market. Also bloodworms is not the best way to fatten up bichirs. Your bichirs looks fine and better shape. Just to let you know that fat bichirs dies early, than bichirs with the girth just a little thicker than the girth of it's neck. Keep your bichirs sexy and healthy, not fat.