You can buy actual turtle food at the pet store.
It is large cubes of semisoft food.
My boyfriend kept sliders for a long time, and he said
they really relished cooked chicken!
Perhaps try that!
Im glad you are aware of how big sliders get,
as most people buy them under the assumption that
these tiny turtles stay small, not knowing they can get like
12+ inches across on the shell!
Dont worry about them being Illegal, every pet store in north america
pretty much sells them. I actually make a point of asking
the employees in Pet Stores if they are aware selling Red Ear Sliders
is illegal and can carry upwards of a 150,000 dollar fine! They usually look shocked and amazed and no, were not aware at all!
So it is quite obvious that despite the illegalness of these critters, that the fish and wildlife administrations are not checking fish stores for them.