I don't know if you still need info,but here is my two cents worth anyway!

I used a automatic feeder once and it worked fine. (I didn't trust it and had a backup plan, but the backup wasn't needed.)

You can as suggested, put some feeder fish in the tank. Also, those weekend feeder blocks for fish work well with turtles too!
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0.1.0 ornate box turtle
1.0.0 eastern box turtle
1.0.0 Yellow belly slider
0.1.0 Red belly cooter
0.1.0 Australian shepard
1.11.0 chickens
1.0.0 Dutch(rabbit)
3.2.0 children (do I still count the married ones?)
1.0.0 husband