I actually have 2 turtles, (not to get off topic).
(BTW if anyone knows what to do with 2 big florida river cooters please let me know!!! My son who went to college brought them back from florida some 5 years a go. I understand they can live 30 years. I know, don't purchase pets you can't care for, but my son was somewhat sad at the time and really enjoyed reptiles. Anyway these turtles are very healthy and easy to care for, but a bigger tank would be best, and we can't release them because they are from florida and we live in ct.)
So getting back to the fish thing. I feed my turtles feeders, and for some reason they did not eat them all. We have 2 feeders that ae now several inches. BTW the water quality is often filthy, but the feeders do fine, they actually eat the turle pellets.
I also keep a tiger and red oscar in another tank.
-R.M.