Getting the Common Snapping Turtle to Eat Better?

Hello, my friend cares for a common snapping turtle at his rescue. It is small, maybe 5 inches round. It is 5 years old so that seems small. It's in a 20 gallon tank, has a uvb and heat lamp, rocks, underwater basking platform thing, and an aquatic turtle filter. It's only been fed frozen blood worms by hand its entire life.

We are trying to help it grow and learn. We tried offering minnows and it made friends with them. We tried dropping the frozen cubes of blood worms in the tank so they would float and he would chase them but he won't eat them. We tried leafy greens and he doesn't care.

Any tips on helping him figure out how to eat without a blue nitrile glove holding metal tongs bringing frozen worms his way?