Hi welcome to the forum
I have 2 Mississippi map turtles in my 40 gallon tank (around 150 litres). They are still very small and so cute
what turtles is it that you have?
My other tank is 125 gallons (450 litres) and has a 5 inch Ornate bichir and a 3 inch or so Lima shovelnose catfish.
You will soon notice that this forum is full of experienced and very knowledgeable members that will be more than happy to help with any questions you may have. They have helped me out with numerous questions.
1 thing I will say is I didn't realise you could keep and sort of fish with turtles. Turtles are meant to be able to attack fish with ease... I may be wrong. Maybe someone here can give you a definite answer