If you're feeding a good quality flake and feeding variety, you're fine.
For example, Hikari Betta Bio Gold has 38% crude protein, 4% fat and 3% fiber. Hikari Tropical Micro Wafers have 44% Protein, 8% fat, and 2% fiber. Fluval Tropical Flake (which actually has pretty good ingredients) has 44% protein, 6% fat and 2% fiber. So the protein and the fat are a little higher and the fiber a little lower. But if you supplement with something like the spirulina brine shrimp that Hikari sells you'll make up for the fiber and add a lower protein treat. If you don't want to do the spirulina brine adding some veggie flake is another option, I used to buy the marine fish ones because they were better quality than what I could find for fresh water fish. In a large tank he's going to be more active, as other's have said, so the extra protein may actually do him good. In the wild they're likely to be spending most of their time eating inverts, so a lot of protein is quite natural to them.
For example, Hikari Betta Bio Gold has 38% crude protein, 4% fat and 3% fiber. Hikari Tropical Micro Wafers have 44% Protein, 8% fat, and 2% fiber. Fluval Tropical Flake (which actually has pretty good ingredients) has 44% protein, 6% fat and 2% fiber. So the protein and the fat are a little higher and the fiber a little lower. But if you supplement with something like the spirulina brine shrimp that Hikari sells you'll make up for the fiber and add a lower protein treat. If you don't want to do the spirulina brine adding some veggie flake is another option, I used to buy the marine fish ones because they were better quality than what I could find for fresh water fish. In a large tank he's going to be more active, as other's have said, so the extra protein may actually do him good. In the wild they're likely to be spending most of their time eating inverts, so a lot of protein is quite natural to them.