I have 2 red eared sliders. they eat carps! or whatever they can catch! It's not a good idea to put your turtles into the aquarium, first off, they need basking place where they can dry off their shelves, secondly, their waste are told to toxic the water. Then thirdly, like what I've just said, they can have fish for tea. So if you can look up any harmless turtle for aquarium and manage to make a place for them to climb over, there you go. But As they grow large, you can encounter loss of fish, and repltiles waste a lot. So better look up in several other sites. as the TT forums or you local pet store be4 mixing the turts with the fish.
In my own opinion, it's better for you to keep turtles in their own tank!
Hope that helps, if you have any more question, just ask. We'll answer if we know ^^