After many years with lots of ‘interesting’ foodsIncluding homemade and raw, I am perfectly happy with Butchers, preferably the tripe loaf mix. Their poops are perfect.
At eight months , he’s ready for adult food. I follow the quantities on the tin, or a bit less. We no longer have cockers. One of mine is a small dog weighing only 7kg, and has one tin total per day. My sons one is 17kg, and has one and three quarters total per day. They came to us as mangy rescue dogs, and are now healthy, shiny and very lean as they should be. I asked the vet if they were underweight, and he said definitely not, unlike the rest of the waiting room.
12 kgs puts Halo half way between, so I would think that with tins , not trays, you could use One and a third of a tin, though the bottom is all jelly. It is mostly water, and mine rarely drink much. One thing I wasn’t happy with dry food was that the body must strain when it’s begging for water to rehydrate the kibble. I wouldn’t like to live on dried meals!
Also, any wet food is bigger and more appetising than a handful of kibble. I think that the dry food suggested at 300gm was far too much. My old springer at 24kg had that amount.
I don’t bother mixing, so can’t help there. I have to stick to grain free so just add fruit or veg.
Hope this helps.