At that size, my three-toed ate earthworms just fine. That's my suggestion. Put the worms and the turtle in the same containter together - that way the turtle won't lose the worms.
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Least favorite quotation: "These foul and loathesome animals are abhorrant because of their cold body, pale color, cartilaginous skeleton, filthy skin, fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, and terrible venom; and so their Creator has not exerted his powers to make many of them." - Carolus Linnaeus