My Salifert is testing positive for nitrites. I am testing it again w/ Fastest. I had a problem w/ my Salifert ammonia test last weekend so I bought a new kit and it checked fine. Could I have a bad test kit?
Nice, you answered your own post
Sometimes test kits mess up based on user error. I myself have done it tons of times. If you think a test is erroneous by all means test it again. After a while you will get to "know" your tank and won't necessarily need to test it unless you make drastic changes such as adding a couple of fish, inverts, or corals...