I am growing some vegetables in my garden and I also have a pond where some turtles and fish live together. I thought maybe when I change the water of my pond could I use that water to irrigate my vegetables? I know that fish and especially turtles can contain bacteria and other parasites so those can also infect my vegetables and even worst, if we eat some of the vegetables could be harmful to our health?
You only need to be worried about some pathogenic e coli that can be incorporated into plant tissues. And generally these are not found in aquatic environments. The other bacteria, viruses and amoebae can be washed off. In all cases, all are destroyed in cooking.
People use fish ( unsure about turtles ) in aquaponics systems where the waste water is filtered by plant roots, and I've not heard of any disease outbreaks with this growing method.
That depends on if you eat vegetables raw, and how paranoid you are. Properly cooked veg should not be a problem. If you are paranoid, just don't put pond water on root vegetables, or cook them well.
Turtles can also carry salmonella.