I had a pet store employee insist that nitrates should always be at 0 in a cycled tank. I told him that my aquarium is planted so I generally keep it between 10-20 ppm. He asked how often I do water changes and I said about 25% every 3 days to keep nitrates down.
He then proceeded to tell me that those water changes were removing the good bacteria that process nitrates. I could barely hold in the guffaw. So, I asked him what those process into. You know, since ammonia gets turned intro nitrites and nitrites get turned into nitrates, what do nitrates get turned into? *dead silence*
Then proceeded to tell me I shouldn't buy fish because their fish were accustomed to nitrates at 0. Bought a plant so I would have a water sample. Tested at 80ppm nitrates. 0.25 ammonia, 0.25 nitrites.
Just so much awesome. Wonder if he's ever thought of sticking a test strip in his own tanks? lol