Sounds like it’s best if Murtyle moved on.
No, all 7 of my turtles ignore the fish, including the wood turtle. Even if they did get some I have so many I don’t worry about it. Of course when I am out there they are all focused on me. Even when they don’t see me though, they tend to be basking or just cruising around.
All the terrapins were/are in ponds with fish their whole lives and being fed by me. If I put I wild caught one in there I am guessing all bets are off.