Fish in a Turtle Tank?

I get asked frequently, whether one could put turtles into a

PUtting a turtle into a tank designed for fish has several problems:
1) Most fishtanks don't have a land area where the turtle can get out.
2) In most fishtanks, the water-level is inappropriate for turtles.
3) In most fishtanks filtration is inadequate to support the addition of turtles.
4) The turtle will eat the fish.
5) The turtle will eat the plants.
6) If this is a natural aquarium, the turtle will dig in the gravel and make
a mess. It may also ingest the gravel, which can lead to problems.

If you wish to keep turtles and fish together, set up a turtle
environemnt , then add the fish. Since most turtles will try and at least partially
succeed at eating the fish, provide hiding places for the fish. In
addition, the fish must be hardy and tolerate a range of water qualities
and temperatures. Personally, I have only kept goldfish with my turtles.
I usually start out with about 2 dozen, of which about half will
survive for about a year.

The advantages of having the fish in there are:
* The fish eat leftover food (I don't feed the fish).
* The fish are a cheap water quality monitor (if the fish are healthy, water quality
is at least acceptable).
* The fish can provide an emergency food supply for the turtles.
* The fish provide turtles with entertainment and exercise (of which most
captive turtles don't get enough).