concern number 1 : the turtle eat the fish
concern number 2 : the fish beat up on the turtle ( is what happens to mine)
concern number 3 : you have to be really careful of bloat with the fish because of the turtle food.
it is not recommended, however I was warned about this from people of the site. as you can see I did it anyhow and he does fine with them. I figured aggression levels of both are about the same. my turtle hasn't even looked at the fish like he want to eat them and I keep a stinkpot musk turtle. I do at times however feel as I need to remove the turtle because he is scared to death of my Africans.
You can find my video of them here
Edit- forgot to tell you I keep mild aggressive except my bumble bees. I wouldn't keep a stinkpot with anything more aggressive my bees (mostly the male) beats up on it. If you do try it make sure you can re home it if needed. I also would like to add a stinkpot doesn't get very big and that's another reason why I figured it will be ok. Most Africans will get to big for them to fit into the turtles mouth. Other turtles that get much bigger may be a threat to the fish I wouldn't know.