Ideal nitrates, and what is acceptable are two different things. You'll find many people here who thing that you must have <40ppm or its horrible for your fish. In reality, while that may be best, it's not always possible and you just need to provide the best you can. Humans do best in the pure air of the Montana mountains where it is free of pollutants, yet many more people live just fine in SoCal where the air is full of smog. What is ideal isn't always what happens, but it's always a good goal to strive for.