depends on temperement really
i had a bunch of sajica X convict hybrids i was culling in my turtle tank and one of them survived and lived for 4 years.
thought it was a turtle! he was such a character but i moved him in with the 11" mayan as he was hastling the tank he was in (a different one) and he got destroyed. which is strange cause he lived with the mayan before perfectly.
however i have an african sidenecked turtle who will strip a fish (4"er) down the the bone in about 2 minutes. turtles are very affective fish eaters so unless you are really confident and dont mind loosing the odd fish here and there, and pick some likely to be compatable species, then go for it.
my guess would be
mississippi map (not too aggresive in my experience)
with some lesser aggresive cichlid like a blue acara or something of that larger size and peaceful nature.
that way as long as the turtle is well fed and has somewhere to bask coexistance can be quiete simple