Fromm makes several different varieties
They have a 4 star line up that is fairly decent food but does contain grains.
They are a family owned/run business that is trusted. No recalls as far as I know.
They do not use ethoxyquin or citric acid or questionable ingredients
They also carry a grain free formula called surf n turf
all their products contain quality ingredients & have balanced calcuim/phos ratios
The kibble is really small but my dogs love it, even my Mastiff.
The price is very reasonable and they ususally have a frequent buyer plan
where you buy 9 and get the 10 bag free
Merrick --cost is a little higher than Fromm, although nowhere near that of the top premium brands
Obviously the cal/phos ratio isn't of a high concern with your dog because he is 6 yrs old,

so Taste of the Wild is an option as well, especially since I've heard they are transitioning to no longer use Ethoxyquin (preservative/pesticide)