I have never heard of housing turtles and fish in the same aquarium. I would assume it's probably not the best idea. Depending on what type of fish you have it is safe to home aquatic frogs with the fish as long as the tank is large enough for both the fish and the frog to be comfortable. Remember, one inch of FULL GROWN fish per 1 gallon of water MINIMUM if you want your fish to be happy and healthy

Beware, a friend of mine had a male betta and a frog in the same aquarium The betta constantly attacked the frog. So be sure the kind of fish you have are compatible with the frog