A varied diet including Pellets, shrimp, cut fish and whole fish is better.. Shrimp alone lacks required vitamin and mineral content. Unless you supplement it you have a diet that is lacking for proper maintenance of the fish...
my spotted refused any pelleted or prepared foods.
I made my own mixture one time that it accepted very hesitantly.
Frozen smelt (silversides), shrimp, tilapia were my main foods.
All of my gar will eat just about anything. Their staple diet is Hikari floating pellets and raw shrimp (with many other treats mixed in). Food never goes uneaten in my gar tank.