Mine loves to eat mysis shrimp. The brine shirmp was ok, but they didn't attack it like the mysis shrimp, plus its more nutrious for them anyways. Try a mixture of brine, mysis, cyclo-peez, flakes and so on. Switch on and off every few days.
Just think of what you like to eat and apply it to them. Would you eat the same thing everyday? Nope...