Eastern box turtles usually don't like fish much unless they are in need of protein or something in there diet. They will eat fish but it is like feeding a kid brussel sprouts.
Also you may want to microwave the fish a little to rid it of any worms or other parasites.
The true gulf coast box turtles from the lower areas of the Apalachicola and coastal areas near there in FL will take fish a little more. They are more aquatic in there habits as they will walk under shallow water to feed on snails and other stuff in the water.
If you try a dark fish like sardines and or tuna and maybe salmon almost all of the box turtles tend to take these better.
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Noah was the first snake collector. ~Eric~