What the pH should be in water for tropical fish to survive?

Different varieties of fish thrive best in different pH readings. In general, a community tropical aquarium should be kept around 7.0; goldfish and livebearers such as guppies like 7.5; angelfish and tetras, 7.2-7.5; mollies and sWordtails, 7.2 to 7.5. Your best bet is to buy a pH test kit from the pet store and test the pH in your tank's water. However, I find that my tanks maintain good pH just with regular maintenance, so I don't test pH unless I suspect a problem.