I tried the 6 fish formula for mine a while ago. On paper it's amazing but it didn't suit them, it was impossible to find a balance between over feeding them and them having diarrhea and feeding enough to keep weight on them.
I used Acana Pacifica (made by the same company but with a 60:40 ratio of meat to fruit/veg rather than 80:20) and they did really well on that but occasionally it would be quite difficult to get hold of.
I now feed Millies Wolfheart countryside mix (one gets a mix of that and the salmon & veg) and I'm really impressed with it, I can't speak highly enough of it.
Our dog loves Orijen although we've had to switch him to the old dog version because he was getting too fat (he's only little, it's easy to give him too much of the normal version as I can't be arsed weighing it!). He's always been really healthy on it, lovely coat and loads of energy.