I purchased a 10 gallon, set up, used tank, for a quarantine tank. The seller said it was set up for over a year. It has 3 Buenos Aires tetras. The seller also said they never changed the water, just added some when it got low. I got it home and tested the water. 0ppm Amonia, 0ppm Nitrites, PH 8.4, and 0ppm nitrates. I would have thought the nitrates would have been very high. And KPH 9 drops. I was wondering if in fact it was cycled? I did a 75% water change and tested two days later, 0 ppm Amonia, 0ppm Nitrites and 0 ppm Nitrates. Ph lowered to 7.8. There was some algae in the tank, but not over loaded. Do you think it is cycled?