Solid Gold is a good food line. Lots to choose from. I think it is important to use their Sea Meal supplement on top of the dry food. I have used their L/R Hundnflocken many years ago with favorable results.
Personally I like CANIDAE dog food and Vibrant Pets Supplement
Although it is considered one of the better commercial, processed foods, I personally don’t recommend Solid Gold. The quality of the ingredients of any diet are of tantamount importance, and I am not comfortable with their ingredient sources.
Bottom line though is that you should be varying the diet. As long as you don’t rely exclusively on Solid Gold (or any specific food) you will do fine.